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TABLE OF CONTENTS
Item 8. Financial Statements and Supplementary Data

U.S. SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

FORM 10-K

ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF
THE SECURITIES EXCHANGE ACT OF 1934

For the fiscal year ended June 30, 2003

Commission File Number: 000-31979

Array BioPharma Inc.
(Exact Name of Registrant as Specified in Its Charter)

3200 Walnut Street, Boulder, Colorado 80301
(Address of principal executive offices)

(303) 381-6600
(Registrant's telephone number, including area code)

Securities registered pursuant to Section 12(b) of the Act: None

Securities registered pursuant to Section 12(g) of the Act:
Common Stock, Par Value $.001 Per Share

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ý    No o

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of registrant's knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K. ý

Indicate by check mark whether the registrant is an accelerated filer (as defined in Rule 12b-2 of the Exchange Act). Yes ý    No o

The aggregate market value of voting stock held by non-affiliates of the registrant as of August 29, 2003 was approximately $128,903,931. (For this computation, the registrant has excluded the market value of all shares of its common stock reported as beneficially owned by executive officers and directors of the registrant; such exclusion shall not be deemed to constitute an admission that any such person is an "affiliate" of the registrant.)

Number of shares outstanding of the registrant's class of common stock as of August 29, 2003: 28,270,415.

Documents incorporated by reference:

Portions of the registrant's definitive Proxy Statement for the 2003 Annual Meeting of Stockholders—Part III

TABLE OF CONTENTS

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        This annual report filed on Form 10-K and other documents we file with the Securities and Exchange Commission contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 that involve significant risks and uncertainties. In addition, we may make forward-looking statements in our press releases or in other oral or written communications with the public. These statements do not relate to historical matters and reflect our current expectations concerning future events. Therefore our actual results could differ materially from those anticipated in these forward-looking statements as a result of many factors. These factors include, but are not limited to, our ability to achieve and maintain profitability, the extent to which the pharmaceutical and biotechnology industries are willing to collaborate with and fund third parties on their drug discovery activities, the ability of our collaborators and of Array to meet drug discovery objectives tied to milestones and royalties, our ability to continue to fund and successfully progress internal research efforts and to create effective, commercially viable drugs, and our ability to attract and retain experienced scientists and management. We are providing this information as of the date of this report. We undertake no duty to update any forward-looking statements to reflect the occurrence of events or circumstances after the date of such statements or of anticipated or unanticipated events that alter any assumptions underlying such statements.

PART I

Item 1. Business

Overview of Array's Business

        We are a drug discovery company creating small molecule drugs through the integration of chemistry, biology and informatics. Our experienced scientists use the Array Discovery Platform®, our integrated set of drug discovery technologies, to invent novel small molecule drugs in collaboration with leading pharmaceutical and biotechnology companies and for our own pipeline of proprietary drug candidates.

        The pharmaceutical industry has an ongoing need to fill their product pipelines with quality drug candidates. In-licensed drugs accounted for nearly a third of pharmaceutical company revenue in 2001. We believe this percentage will increase and the value of in-licensed clinical candidates will escalate. In addition, recent advances in biology, including the sequencing of the human genome, have revealed thousands of additional potential drug targets that can be modulated for the treatment of disease. As a result of the proliferation of new targets, we believe the drug research and development bottleneck is shifting from the identification of new targets to the creation of safe and effective therapeutics.

        As a small molecule drug discovery company, Array is well positioned to benefit from each of these trends. We believe small molecule drugs, typically invented by chemists, have inherent advantages over other types of therapeutics, such as protein-based drugs. Advantages include a greater universe of treatable diseases, lower cost with greater ease of manufacturing, and patient preference for a pill over an injection. Although a high proportion of biotechnology research has historically been devoted to protein-based therapeutics, approximately 87% of the top 100 prescription drugs, based on worldwide sales in 2002, are small molecule drugs. Accordingly, we believe that there will be increased emphasis on small molecule drug discovery in the biotechnology industry.

        Our mission is to be the industry leader in small molecule drug discovery by utilizing the Array Discovery Platform to efficiently create high-quality drug candidates. The Array Discovery Platform is a fully integrated drug discovery capability containing technologies necessary to create a drug candidate. Early in the drug discovery process, our scientists engineer into a drug candidate desirable drug characteristics, such as improved potency, specificity and dosing regimen and reduced side effect profile. We believe that the early optimization of superior drug characteristics will reduce the failure rate of drug candidates, thus increasing research productivity.

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        To capitalize upon opportunities in drug discovery, we believe that an experienced scientific team with a track record of success in drug discovery is crucial. Accordingly, we have grown our staff to 244 full-time employees as of June 30, 2003, including 183 scientists, of whom 106 have Ph.D.s and 74 have experience at large pharmaceutical or biotechnology companies. Members of our scientific staff have contributed during their careers to more than 20 Investigational New Drug applications, or INDs, and are inventors on over 200 drug-related patents and patent applications and are authors on over 1,100 scientific publications.

        Our objective is to build the industry's premier drug discovery company by:

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Continuing to enhance the Array Discovery Platform by developing novel tools and implementing new technologies to be the industry's most efficient inventor of small molecule drug candidates;



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Identifying drug candidates in collaboration with leading pharmaceutical and biotechnology companies, where we receive research funding and share in the success we create through potential milestone and/or royalty payments; and



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Continuing to fill our pipeline of proprietary drug candidates, which we will license for co-development and commercialization with pharmaceutical and biotechnology partners.

        Our fiscal 2003 achievements include:

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Increasing revenues to $35,125,000, a slight increase compared to $35,089,000 in fiscal 2002;



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Initiating research collaborations with InterMune, Inc. and GenPath Pharmaceuticals, Inc., that include research funding and potential milestones and/or royalties;



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Increasing investment in Array's proprietary research to $11.2 million, compared to $5.5 million in fiscal 2002



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Advancing the MEK program into development with an anticipated IND filing in fiscal 2004



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Moving two other proprietary programs into early preclinical testing, for cancer and inflammation indications with the expectation of nominating a clinical candidate from one of these programs in fiscal 2004



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Progressing other proprietary programs that are in lead generation, with plans to move select programs into lead optimization in fiscal 2004;



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Successfully completing Array's first in-house cGMP manufacturing campaign, producing bulk quantities of Array's proprietary MEK drug candidate for development through Phase I clinical testing;



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Initiating research in our new pharmacology unit, a capability that includes early toxicity, pharmacology and drug metabolism testing to determine the safety and efficacy of compounds, and that will accelerate both collaborative and proprietary research programs;



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Completing the renovation of 48,000 square feet of newly acquired laboratory space, bringing Array's total facilities to 165,000 square feet;



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Strengthening corporate governance with the appointment of Gil J. Van Lunsen, former Managing Partner at KPMG LLP, to Array's Board of Directors, and as Audit Committee chair. In addition, Array's Corporate Governance, Audit and Compensation Committees were reorganized to include only independent directors; and



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Hiring additional experienced scientists from major pharmaceutical and biotechnology companies and top universities; we employ 183 scientists, including 106 Ph.D.s, as of June 30, 2003.

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Drug Discovery and Development

        Drug discovery and development is the process of creating and evaluating drugs for the safe and effective treatment of human disease. This process requires biological, chemical and informatics expertise. The role of biology includes understanding the mechanism of diseases, identifying potential targets for therapeutic intervention and evaluating potential drug candidates. Chemistry's role includes the invention of safe and effective new chemical entities, or drug candidates, to address these targets. Informatics improves decision-making by identifying and replicating the characteristics of successful drugs, efficiently sharing current knowledge and creating databases to predict future clinical success. The drug discovery and development process encompasses the following:

        Target identification.    Targets are proteins that may play a fundamental role in the onset or progression of a particular disease. Biologists identify targets against which chemists create drug candidates. Until recently, pharmaceutical researchers were limited to studying approximately 500 biological targets. This number is being vastly expanded through genomics. Pharmaceutical and biotechnology companies are advancing many of these newly identified potential targets into drug discovery. Many other potential targets have yet to be validated, meaning that their roles in disease have yet to be established or understood.

        Drug discovery.    Drug discovery includes structural biology, lead generation, lead optimization and process research and development.

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Structural biology.  Structural biology is the process of cloning, expressing and purifying protein targets to create information about their functions and how they interact with drug candidates.



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Lead generation.  Lead generation is the process of identifying lead molecules that interact with a target with sufficient potency and selectivity to warrant further testing and refinement as possible drug candidates. During lead generation, researchers develop tests, called assays, to screen libraries, or large collections of potential lead compounds, against targets to evaluate their therapeutic value.



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Lead optimization.  Lead optimization is the iterative process of refining the chemical structure of a compound to improve its drug characteristics with the goal of producing a preclinical drug candidate. Researchers focus on a number of considerations in optimizing a drug candidate, including the following drug characteristics:

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Process research and development.  In the earlier stages of drug discovery, small, typically milligram quantities of the compound are used. Before a drug candidate can be taken into clinical trials, larger, typically kilogram quantities often must be synthesized. The goal of process research is to streamline the synthesis of larger quantities of the compound by minimizing the number of synthetic steps chemists must perform and reducing the time and cost of production. Once a successful process is developed, batches of compounds produced in accordance with

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cGMP processes are synthesized for animal and human testing in the preclinical and clinical development phases.

        Preclinical development.    Prior to human clinical testing, potential drug candidates undergo extensive in vitro, or laboratory, and in vivo, or animal model, studies to predict human drug efficacy and safety. These studies investigate efficacy and toxicity over a wide range of doses and the mechanism by which drugs are metabolized. The objective of preclinical testing is to obtain results that will allow selection of a clinical candidate to enter human clinical trials through approval of an IND application by the FDA. Preclinical development often coincides with lead optimization.

        Clinical development.    Clinical trials, or human tests to determine the safety and efficacy of potential drug candidates, are typically conducted in three sequential phases, although the phases may overlap. Successful clinical trials will result in the filing of a New Drug Application, or NDA, with the FDA in order to obtain approval to market the drug in the United States. Similarly, clinical trials must be conducted and regulatory approvals secured before a drug can be marketed in other countries.

Issues and Opportunities in Drug Discovery

        The drug industry's need to fill product pipelines.    The pharmaceutical industry has an ongoing need to fill their product pipelines with quality drug candidates. Faced with actual and impending loss of patent exclusivity on several important products, generic competition and cost containment initiatives from government and private healthcare providers, both pharmaceutical and biotechnology companies are under severe pressure to bring additional drugs to market. We believe this need creates significant opportunities for licensing high-quality drug candidates and entering drug discovery collaborations.

        Need for improved research productivity in drug discovery and development.    Despite the recent technological advances and investment in genomics, biology, chemistry and informatics, drug research and development remains slow, expensive and risky. Estimates indicate that annual research and development spending more than tripled from 1993 to 2002, while the number of new drugs approved by the FDA during the ten years ended in 2002 only increased by 36% over the ten-year period ended in 1992. We believe this disparity provides a significant opportunity for a drug discovery organization that can efficiently create higher-quality drug candidates resulting in reduced attrition in clinical development.

        The challenge of turning genomics information into drugs.    The research and development process is experiencing a fundamental change fueled by the revolution in genomics, which has resulted in the identification of many new potential drug targets. We believe the resulting proliferation of targets from 500 to between 3,000 and 10,000 has shifted the bottleneck in drug research and development from the identification of new potential drug targets to the creation of safe and effective drugs for these targets. We believe the knowledge gained from genomics and biology and the resulting drug discovery bottleneck, coupled with the advantages of small molecule drugs, will lead to increasing investment in small molecule drug discovery.

        Importance of chemistry in the drug discovery process.    The chemical make-up or structure of a drug is the key determinant of its potency, specificity, dosing regimen and side effect profile. Minor modifications in chemical structure can differentiate drugs and determine their success or failure in the marketplace. While targets are used for evaluating the drug characteristics of chemical compounds, chemistry is necessary to invent the composition of the actual drug. Therefore, while the ultimate value of intellectual property associated with newly identified targets is currently unknown, the value of intellectual property associated with drugs invented by chemists is known to be significant.

        Need for drug discovery capabilities within the biotechnology industry.    Many biotechnology companies are increasing their focus on creating drugs against their proprietary targets. Historically,

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they have partnered with pharmaceutical companies to create small molecule drugs. These arrangements have often resulted in biotechnology companies relinquishing much of the potential economic value resulting from their discoveries. Accordingly, several biotechnology companies have announced their intention to build small molecule drug discovery capabilities internally or through acquisitions. We believe they face significant barriers in creating a competitive drug discovery platform, which include: the difficulty of hiring multidisciplinary teams of scientists with drug discovery experience; the significant investment necessary to build and equip specialized laboratories; the difficulty in identifying and integrating acquisition opportunities; and, most importantly, the opportunity cost in time required to build an effective drug discovery capability.

The Array Solution

        Our solution to address the issues and opportunities in drug discovery is the Array Discovery Platform, our integrated suite of drug discovery technologies, which is designed to increase research productivity through creating higher-quality drug candidates and lowering clinical attrition rates. This platform includes the pragmatic integration of appropriate drug discovery technologies, enabling research tools and knowledge management through an electronic notebook and predictive computational modeling. We utilize predictive computational modeling to improve experimental design and predict favorable drug characteristics. Our experienced scientists focus on data quality, not quantity, creating superior drug candidates through improved decision-making. We believe we have implemented a unique solution to bridge the gap between target discovery and clinical development and to address the issues and opportunities in drug discovery by:

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Hiring experienced scientists and organizing them into multidisciplinary teams;



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Enhancing the Array Discovery Platform by continuing to develop, acquire and integrate appropriate new technologies that emphasize high-quality data generation;



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Creating and utilizing enabling research tools to accelerate the execution of experiments;



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Building knowledge management tools to improve the design of experiments and predict favorable drug characteristics; and



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Identifying lead compounds and designing drug candidates against multiple targets within protein families in a parallel fashion.

        We have assembled a scientific team with experience in both the pharmaceutical and biotechnology industries to implement our solutions. During their careers, these scientists have contributed to more than 20 INDs, and have been inventors on over 200 drug-related patents and patent applications and authors on over 1,100 scientific publications.

Strategy

        Our objective is to become the leading inventor of high-quality drug candidates by building the Array Discovery Platform into the industry's premier drug discovery capability. Our strategies to achieve this objective are as follows:

        Create a portfolio of proprietary drug candidates.    We use the Array Discovery Platform to invent our own proprietary drug candidates against known, commercially valuable targets and expect to increase our investment in our proprietary research efforts. Our focus is on improving current drug therapies, either in clinical development or on the market, for which we have identified deficiencies. We intend to collaborate with biotechnology and pharmaceutical partners to co-develop and commercialize these drug candidates.

        Accelerate the creation of high-quality drug candidates.    Our integrated drug discovery approach simultaneously leverages multiple technologies within the Array Discovery Platform to enable our

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scientists to share knowledge and is designed to improve decision-making across the organization. Our experienced scientists utilize the Array Discovery Platform to invent drug candidates by understanding the complex relationships between chemical structure and desirable drug characteristics. We believe this approach speeds the creation of high-quality drug candidates and will improve success in clinical development.

        Become the drug discovery partner of choice.    We provide collaborators with a fully integrated drug discovery capability to create drug candidates against their targets. While collaborators can access individual components of this capability, we intend to continue expanding collaborations across the entire Array Discovery Platform to become the drug discovery partner of choice.

        Create a world-class scientific research environment.    We expect to grow our business by continuing to recruit experienced scientists. Our continued success in recruiting and retaining these scientists depends upon the maintenance of our culture, which emphasizes quality science, innovation and empowerment of our scientists, and our ability to provide industry competitive salaries and equity participation in our company. We are committed to continuous process improvement, implementation of new technologies, shared learning among our scientists and innovative organizational design.

        Expand our capabilities through internal development and acquisitions.    We intend to acquire or develop new technologies and capabilities to expand the Array Discovery Platform. We have completed construction of a cGMP manufacturing facility, which allows us to produce chemical compounds that meet cGMP requirements in quantities for Phase I clinical trials. In addition, we have added a capability and the necessary expertise to conduct pharmacology and toxicology studies. These additions complete the Array Discovery Platform, providing all the major capabilities required to create a drug candidate for a particular drug target. In the future, we may acquire additional laboratory sites to meet future needs and better attract scientific talent.

The Array Discovery Platform

        We believe the Array Discovery Platform, our integrated approach to drug discovery, enables us to efficiently create higher-quality drug candidates. The Array Discovery Platform includes the following technologies:

        Structural biology.    Our experienced biology teams are creating a better understanding of how small molecule drugs interact with targets. These teams clone, express and purify related families of protein targets across multiple therapeutic areas to gain insights into their function. X-ray crystallography and computational modeling are used to define the three-dimensional structures of these proteins. Utilizing this structural information, chemists can design and synthesize new analogs of lead compounds that are likely to have a better fit with the target protein and improved potency.

        Predictive informatics.    Predicting drug characteristics, such as potency, dosing frequency and potential side effects, requires powerful data mining and management tools. Our informatics teams comprise computational chemistry, scientific computing and medicinal chemistry experts who work together to increase the probability of creating a successful drug. Our proprietary software enables our scientists to search databases of existing drugs, to generate novel predictive databases and to create modeling programs designed to better-forecast drug characteristics. In addition, we use an electronic notebook to allow our scientists to collect and access information directly in the laboratory and throughout the organization. We believe the integration of these technologies improves scientific decision-making, resulting in higher-quality drug candidates.

        High throughput screening.    We develop our own assays, or format assays supplied by a collaborator, for high throughput screens and can screen up to 100,000 compounds per week. These assays are then used to screen tens of thousands of small molecule compounds to obtain quantitative

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measures of drug quality. We also screen selected compounds in metabolism and toxicology assays both to establish quality and to populate our predictive databases. Our computational and medicinal chemists then mine this information to design focused libraries of small molecule drug candidates.

        Cell biology.    Our cell biology group performs screening, including in high throughput format, using intact cell-based assays to complement and extend our biochemical screening capabilities. Cell-based assays allow analysis of compound activity in an environment similar to the one in which a drug would act. We have developed novel functional and mechanistic assays to guide lead optimization efforts during the early drug discovery process. Additionally, the group is responsible for developing biomarker assays, or tests to determine the biological activity of a compound in humans, that may be used in clinical development to identify patient populations and to guide dosing.

        Lead generation.    Our lead generation teams create and identify chemical compounds that demonstrate desirable drug characteristics when screened against a target. Compounds that warrant further testing and refinement as potential drug candidates are called leads.

Optimer® building blocks

        We believe that chemists can create high value compounds more rapidly by using quality building blocks and automated chemical synthesis techniques. We recognize that a constraint in drug discovery is the availability of these high-quality building blocks. Our chemists have used our proprietary software, RADICAL, and their experience in assessing drug-relevant chemical structures to design a series of building blocks with desirable drug-relevant properties. These building blocks are added to a core chemical structure, or scaffold, during compound synthesis and are an important component of our overall drug discovery strategy. We produce primary building block sets for construction of our Lead Generation Libraries. We then use sets of complementary secondary building blocks for creating focused libraries to determine structure activity relationships, or SARs, in lead optimization programs.

Lead Generation Libraries

        A critical rate-limiting step in the drug discovery process is the availability of high-quality compound libraries that have been designed for screening specifically against important target classes and for subsequent rapid lead optimization. We believe that the production of large compound libraries, by itself, has limited value for creating high-quality leads. Instead, we design our libraries so that any leads require less optimization. We believe this approach will result in clinical candidates with a greater likelihood of clinical success.

        We design our libraries according to the following criteria:

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Biologically-relevant diversity.  We have established specific computational parameters to define the diversity of our compound libraries. Our proprietary informatics tools categorize how changes in chemical structure correlate with the biological activity of known drugs and use this information to define our diversity parameters. Libraries can be constructed to optimize diversity and therefore maximize the information provided by each library compound.



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Maximize unique pharmacophores.  Our scientists maximize the number of distinct three-dimensional drug-like shapes, or pharmacophores, during library design. This approach is designed to optimize the number of discrete compound sets within a library, with the goal of identifying the key structural features of drug-target interactions.



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Target-directed chemical scaffolds.  Our chemists create scaffolds designed for disease-related families of targets. We believe this scaffold strategy allows us to increase the probability of finding a high-quality lead for a given target. We attach our novel building blocks to these scaffolds to create our library compounds.

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Drug-relevant building blocks.  We use drug-relevant building blocks to synthesize libraries. We design the library to identify the least complex structure that will interact with a target. Any lead generated from our Lead Generation Libraries can be readily optimized through the use of more complex building block sets. These focused libraries provide initial SAR around any lead.



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Optimized chemical synthetic processes for high purity.  We invest significant effort in the process design and synthesis of each library to ensure that the compounds generated are highly pure and can be readily optimized. The library undergoes analysis during each stage of its development to ensure the identity of each compound and maintain overall quality.

        High-purity compounds are critical to the success of high throughput screening strategies in lead generation. Low-purity compounds result in a higher proportion of false leads, which waste discovery resources. Our analytical chemistry teams use automated instrumentation to evaluate the purity of chemical compounds, analyze the chemical processes used to synthesize these compounds and measure important drug properties. This capability allows for the high throughput analysis and purification of thousands of compounds per week.

        We provide chemical compounds from our Lead Generation Libraries to our collaborators under a non-exclusive license for internal research. We also synthesize custom libraries, which we typically offer on an exclusive basis to individual collaborators, focused on specific target families or our collaborators' proprietary scaffolds. We retain all other rights to the compounds in our Lead Generation Libraries, including the right to use these compounds for our internal and collaborative programs, as well as the rights to the synthetic processes used to create these compounds. We create sub-libraries that interact with specific target families, including G-protein coupled receptors, nuclear receptors, enzymes and protein-protein interactions. The majority of all drugs on the market today are aimed at targets within these families.

        Lead optimization.    Leads that interact with targets may come from several sources, including our libraries, rational drug design, scientific literature and our collaborations. Regardless of the source, we apply the same defined processes to optimize these leads to clinical drug candidates. We first utilize information regarding the three-dimensional structure of the target-lead interaction to design novel sets of compounds with the potential for better potency for synthesis. Next, we use our informatics capability to eliminate certain compounds that are predicted to have poor drug characteristics. We then synthesize, analyze and purify this refined set in a parallel format and screen these compounds in select assays to quantify drug characteristics. An iterative process of making small changes in chemical structure, evaluating the results and engineering improvements into the drug candidate is used to optimize its interaction with a target and refine its drug characteristics.

        Pharmacology.    Our Pharmacology group determines the pharmacokinetic profile, potency, efficacy, selectivity and potential toxicity of lead compounds. The group uses pharmacological models, with a specific focus on oncology and inflammation, to evaluate efficacy and dosing regimen of lead compounds. Toxicology testing is conducted to determine the safety profile of a compound early in development. During preclinical development, our Pharmacology group designs and oversees the necessary studies, including regulated safety pharmacology and toxicity testing, for IND application submission.

        Drug metabolism.    When optimizing desirable drug characteristics, it is often critical to determine how drugs are modified by the body at an early stage in the discovery process. We have established a series of assays to identify these metabolic changes. These assays include human liver enzyme assays, cellular assays and assays based upon samples obtained from preclinical studies. We measure both the rate at which compounds are metabolized and how they are metabolized using mass spectrometry and nuclear magnetic resonance. We also screen selected compounds in these assays to build drug metabolism databases to help predict clinical success of our future compounds.

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        Process research and development.    Our process chemists improve complex synthetic procedures to allow for more efficient scale-up and production of drug candidates. We design proprietary processes to lower the cost and increase the rate at which drug candidates can be synthesized. We believe the experience of our process chemists in resolving complex synthetic problems allows us to rapidly develop new synthetic procedures and to accelerate the development of valuable drug candidates for human testing. Our goal is to apply these skills and this experience to create novel yet efficient processes to synthesize complex molecules.

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Process design and scale-up.  Once a potential drug candidate has been identified, it is critical to reach a rapid decision whether to advance the candidate into the clinic. In many cases, lack of an adequate quantity of a specific compound for preclinical testing delays that decision. Our efforts reduce the number of steps in complex medicinal chemistry processes and improve yields to allow for the rapid synthesis and scale-up of preclinical and clinical drug candidates.



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Custom synthesis.  Our chemists undertake challenging syntheses on a custom basis to produce building blocks, complex intermediates and final products in either small scale or bulk quantities. We have synthesized for a number of collaborators increasingly larger quantities of compounds to meet their research needs. We intend to create proprietary processes that can be licensed to collaborators as they advance potential drug candidates into clinical trials. We have the capacity to produce lots of up to 10 kilograms.

        cGMP manufacturing.    Our cGMP manufacturing facility allows us to produce chemical compounds that meet cGMP requirements for Phase I clinical testing. This capability features three cGMP labs, which are used to manufacture kilogram-quantity bulk material and to qualify analytical reference standards and impurities. Array's chemists are skilled in rapidly producing the first qualified lot of an Active Pharmaceutical Ingredient, accelerating the start of human clinical trials.

Proprietary Drug Discovery

        We use the Array Discovery Platform to invent our own proprietary drug candidates. We plan to co-develop and commercialize these products in partnership with pharmaceutical or biotechnology companies to maximize their risk-adjusted value. Our primary research interests are cancer and inflammatory disease. We focus on biologic functions, or pathways, that have been identified as important in the treatment of human disease. Our goal is to efficiently create drug candidates aimed at targets within those pathways that have been validated by drugs that are in development or on the market. Many of these drugs have therapeutic liabilities; we seek to create clinical candidates with improved drug characteristics that overcome the liabilities, providing a competitive advantage. In addition, we may selectively seek to create first-in-class drug candidates against novel targets of broad medical interest.

        Our approach is designed to increase research productivity by taking advantage of the similarities in drug design strategies for related targets within a protein family. We identify disease-associated pathways and access targets within those pathways through publicly available human genomics information and scientific literature. These protein families will typically have similar three-dimensional structures and related biological function and/or enzymatic activity. More importantly, the experimental design expertise required to create drugs against a given target is captured and replicated against the entire target family. In parallel, we synthesize focused compound libraries, which are designed to interact with targets within a family. By screening these libraries against several targets within a family, we seek to generate multiple leads with desirable drug characteristics. Our scientists then optimize the drug characteristics of these leads to provide clinical development candidates.

        We are currently working on a number of target families, including kinases, proteases and certain enzymes, which are important targets for the treatment of cancer, arthritis, diabetes, asthma, Inflammatory Bowl Disease and Chronic Obstructive Pulmonary Disease.

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Oncology programs

        One set of pathways of interest is the cellular proliferation pathways within tumor cells. Several drugs directed against these pathways are now in clinical testing or have reached the marketplace including IRESSA® (gefitinib), Gleevec® (imatinib mesylate) and Herceptin® (Trastuzumab). In one pathway of particular interest, the EGF activation pathway, we have developed proprietary inhibitors of EGFR, ErbB-2, raf and MEK kinase targets. Our most advanced program is directed against MEK, and has yielded a clinical development candidate. With this compound, we have observed no significant adverse effects in early toxicology testing and have demonstrated efficacy in cellular and rodent models of human cancer. We have completed the synthesis of cGMP clinical supplies of our MEK candidate and have initiated regulated safety testing. In addition, we have created a series of select inhibitors in our ErbB-2 program that are now undergoing efficacy studies in models of human disease and preclinical evaluation.

Inflammation programs

        Other pathways of interest involve the biosynthesis of Tumor Necrosis Factor, or TNF. Several drugs that modulate TNF levels, including ENBREL® (etanercept), REMICADE® (infliximab), and Humira™ (adalimumab), have proven effective in the treatment of rheumatoid arthritis and other inflammatory diseases. Our primary TNF biosynthesis pathway of interest is the MKK, p38a and MK-2 kinase pathway. In our p38a program, we have created proprietary, potent compounds, which have demonstrated efficacy in cellular models of TNF production and animal models of inflammatory disease. These compounds arose from a de novo drug design program, using our proprietary molecular modeling techniques and X-ray crystallographic structural data.

        We are also generating leads against additional targets and expect to advance several of them into lead optimization in fiscal 2004.

Commercialization

        We intend to maximize the value we capture by focusing our scientific resources on collaborations that use the full breadth of our capabilities and on our proprietary drug programs that enable us to participate in the success of the drug candidates that we create.

        Our intent is to increase revenue by continuing to expand our collaborations across the Array Discovery Platform. We enter into collaborations with pharmaceutical and biotechnology companies and receive fees for each scientist dedicated to these programs. In addition, in a number of our current collaboration agreements we are entitled to up-front fees, milestone payments upon achievement of certain drug discovery objectives and/or royalties based upon sales of products commercialized by our collaborators as a result of these agreements. We also sell or license research tools, including our Optimer building blocks and our Lead Generation Libraries, on a non-exclusive basis to multiple collaborators, creating a recurring revenue stream.

        We create proprietary drug candidates with the intent of furthering their development and increasing their potential commercial value through collaborations with biotechnology or pharmaceutical partners. In the future, we may choose to advance certain drug candidates as far as early clinical development before entering into a collaboration agreement to maximize the value we retain. As we advance candidates, we will seek collaborations that provide us with an initial licensing fee for exclusive rights to our intellectual property, payments for continued research and down-stream payments that include milestone and/or royalty payments.

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Our Collaborators

        A key element of our strategy is to increase the value we provide collaborators by expanding our relationships with them across complementary development efforts. Below, we describe our most significant collaborations:

        Eli Lilly and Company.    In March 2000, we entered into a research agreement with Eli Lilly to form a chemistry-based research collaboration. Under the terms of the agreement, up to 30 of our scientists provide drug research in collaboration with Eli Lilly scientists on identified Eli Lilly drug discovery projects. We are compensated based upon an annual rate for each full-time equivalent employee working on an Eli Lilly project. Initially, this collaboration focused on certain aspects of our lead optimization chemistry. However, Eli Lilly has since expanded these joint efforts to other aspects of the Array Discovery Platform. Our agreement with Eli Lilly terminates in March 2005, but Eli Lilly may terminate the agreement at any time upon payment of an early termination fee.

        GenPath Pharmaceuticals, Inc.    In June 2003, we entered into a drug discovery collaboration agreement with GenPath to identify small molecule drugs which target a novel tumor maintenance gene discovered in GenPath's proprietary genetic model systems. We believe the Array Discovery Platform will complement the biological discovery technology already in place at GenPath. GenPath will have access to Array's compound libraries, high throughput screening and medicinal chemistry resources. Under the agreement, we will receive research funding and be entitled to receive milestone payments based on the selection and progress of a development candidate. Our research program with GenPath terminates in June 2005, but GenPath may terminate the program earlier upon 90 days' notice.

        ICOS Corporation.    ICOS was our first drug discovery collaborator and has now taken advantage of the entire Array Discovery Platform. Our first agreement with ICOS, initiated in December 1998, addressed lead optimization of up to four ICOS targets. Under this agreement, our scientists, in collaboration with ICOS' scientists, developed clinical candidates from ICOS' preliminary leads. Based upon the success of this program, ICOS expanded our collaboration in the spring of 1999, by both initiating a second lead optimization program on a separate set of targets and subscribing to our Lead Generation Libraries. In less than one year, our initial collaboration led to the development of a clinical candidate, IC485, for a target called phosphodiesterase 4, or PDE4, for the treatment of inflammatory conditions. To speed the development of this clinical candidate, ICOS chose to access our chemistry process research to refine the production process to produce sufficient quantities for preclinical and early phase clinical testing. In November 2001, ICOS announced the initiation of a Phase I clinical trial for IC485, and we received a milestone payment for the achievement of this objective. We are entitled to additional milestone payments upon the achievement of specific clinical objectives.

        In July 2000, we consolidated and expanded our lead optimization agreements with ICOS into a drug discovery collaboration agreement for lead optimization on undisclosed targets. Under this agreement, ICOS has the exclusive worldwide right to develop and market any products resulting from the collaboration. We are compensated based on an annual rate for each full-time equivalent employee working on an ICOS project and are entitled to milestone payments upon achievement of identified development and commercialization goals for products resulting from the collaboration. In March 2001, we expanded this lead optimization agreement and entered into a compound library agreement with ICOS. The research program expired in July 2003, but was extended for one target through December 2003.

        In August 2001, we entered into an additional drug discovery collaboration agreement, to discover and develop small molecule drugs directed at two specific targets containing the I-Domain allosteric site, or IDAS, structural motif. IDAS-targeted drugs regulate function of the target proteins through a novel allosteric mechanism. ICOS identified key structural features of proteins containing the IDAS

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motif that our scientists exploited to systematically produce drugs against targets of this class. Under the terms of this agreement, ICOS provided us with research funding over two years, which ended in August 2003. Our scientists and ICOS' scientists collaborated in all aspects of lead generation and lead optimization. ICOS is responsible for clinical development and commercialization. We are entitled to receive success payments upon reaching certain development milestones and royalties based upon sales of products resulting from this collaboration.

        InterMune, Inc.    In September 2002, we entered into a drug discovery collaboration agreement with InterMune to create small molecule therapeutics targeting hepatitis. This agreement is representative of InterMune's stated strategy to expand their own internal applied research capabilities and efforts, which are focused on exploring new uses for leads and identifying promising drug candidates to build their pulmonary disease, infectious disease and anti-cancer franchises. InterMune funds drug discovery research conducted by us based on the number of scientists working on the research phase of the agreement and will be responsible for all development and commercialization. We are entitled to receive milestone payments based on the selection and progress of clinical drug candidates, as well as royalties on net sales of products derived from the collaborative efforts. Our research program with InterMune terminates in September 2004, but InterMune may terminate the program and the agreement earlier upon 90 days' notice.

        Japan Tobacco Inc.    In March 2002, we entered into a drug discovery collaboration agreement with the pharmaceutical division of Japan Tobacco Inc. to create small molecule therapeutics against a proprietary Japan Tobacco target. Japan Tobacco funds drug discovery research conducted by us based upon the number of Array scientists working on the research phase of the agreement. We are entitled to receive milestone payments based on the selection and progress of clinical drug candidates, as well as royalties on net sales of products derived from the collaborative efforts. The research program will expire in March 2004.

        Merck and Co., Inc.    In May 1999, Merck purchased building blocks from our Optimer collection on a non-exclusive basis. This initial introduction led to an agreement for the exclusive development and supply of custom synthesized compounds for Merck. Building on this relationship, in September 2000, we announced an agreement with Merck for process research, synthesis and supply of custom libraries for Merck's drug discovery programs. Under this agreement we develop processes for the synthesis of each library in collaboration with Merck scientists and utilize our proprietary high-speed synthesis and parallel purification platforms to create these high-quality libraries. Under the terms of the agreement, which expires in December 2003, Merck provides us with research funding as well as payment upon delivery of compounds.

        Pfizer Inc.    In October 2001, we entered into a compound library agreement with Pfizer, which expires in October 2003, to provide non-exclusive access on a per-compound fee basis to compounds in our Lead Generation Libraries for Pfizer's internal lead generation efforts. Pfizer has the option to gain exclusive rights to compounds upon payment of either a one-time activation fee or annual fees. We retain all ownership of the intellectual property rights to the compounds and to our Lead Generation Libraries as well as any inventions made by our scientists working under this agreement. This agreement is terminable only upon breach or insolvency of a party.

        Takeda Chemical Industries, Ltd.    In July 2001, we entered into a lead generation collaboration agreement with Takeda to create a series of small molecule drug leads against a proprietary Takeda target. Takeda pays us fees based upon the number of our scientists working on the research phase of the agreement. We are entitled to receive success payments based upon the attainment of certain development milestones and royalties based upon sales of products resulting from the collaboration. The research program will expire in July 2004.

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        Compound library agreements.    We have entered into agreements with customers, including Tularik in June 1999, which Tularik extended in January 2000, and which will expire in 2005; DuPont in August 2000, which expires in December 2005; Hoffmann-La Roche Inc. in June 2001, which expires in June 2006; and Pfizer in October 2001, which expires October 2003, to provide non-exclusive access on a per-compound basis to compounds in our Lead Generation Libraries for their internal lead generation efforts. These customers have the option to gain exclusive rights to compounds upon payment of either a one-time activation fee or annual fees. We retain all ownership of the intellectual property rights to the compounds and to our Lead Generation Libraries as well as any inventions made by our scientists working under these agreements. These agreements are terminable only upon breach or insolvency of a party.

Business Development

        To date, our business development activities have been conducted primarily through direct customer contact by our senior management and scientists and through customer referrals. Because our collaborators are primarily skilled scientists, we use our scientific expertise to initiate and build strong customer relationships. We have relied upon the services of a consulting company, Transpect, Inc., to aid in our business development efforts in Japan. We market our Optimer building blocks through multiple channels, including targeted mailing of a hard copy catalog and through an Internet catalog. We plan to continue to grow our business development resources.

Research and Development

        Our research and development expenses have increased each year since our inception. The following table shows our research and development expenses since inception for our collaborators and for our proprietary drug discovery programs.

(*)

Excludes compensation expense related to option grants

        We are currently conducting research and development in the following areas:

        Assay development and high throughput screening automation.    We are investing in the development of new assay and high-speed screening technologies to more effectively evaluate potential drug compounds for their therapeutic value, including specificity and metabolism, and to increase our screening capacity.

        Informatics.    We are continuing our development and enhancement of database technology to more effectively capture, organize and link the data generated by our scientists and to make this information more seamlessly accessible for any of our drug discovery efforts. In addition, we continue the development of internal software technologies designed to increase the speed and efficacy of our lead generation and lead optimization chemistry.

        Libraries.    We have ongoing projects to develop and refine technologies necessary to create high-quality compound libraries composed of drug-relevant compounds that can be rapidly optimized. Our research is focused in the areas of designing drug-relevant building blocks and scaffolds,

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maximizing drug-like characteristics of our library compounds, optimizing library synthesis processes and maximizing biologically-relevant compound diversity.

        Proprietary drug discovery projects.    We expect to continue to invest in internal drug discovery programs intended to create a pipeline of proprietary drug candidates. We intend to co-develop and commercialize any resulting drug candidates through collaborations with pharmaceutical and biotechnology companies.

Competitors

        Competition across the range of our drug discovery focus is currently fragmented. We compete with a number of companies in each of the functional areas of drug discovery that we serve. Our major competitors among medicinal chemistry outsourcing companies include: Albany Molecular Research Inc.; ArQule, Inc.; Discovery Partners International, Inc.; Evotec OAI; and Tripos, Inc. Our major competitors among drug discovery companies include: Celgene Corp.; OSI Pharmaceuticals, Inc.; Tularik Inc.; and Vertex Pharmaceuticals Incorporated. In addition, we compete with the internal research departments of biotechnology and pharmaceutical companies. Many of these companies, some of which are our collaborators and some of which represent market opportunities for us, are developing or already possess internally the technologies we offer. Academic institutions and other research organizations are also conducting research in areas in which we provide our capabilities, either on their own or through collaborative efforts.

Government Regulation

        In the course of our business, we handle, store and dispose of chemicals and biological samples. We are subject to various federal, state and local laws and regulations relating to the use, manufacture, storage, handling and disposal of hazardous materials and waste products. These environmental laws generally impose liability regardless of the negligence or fault of a party and may expose us to liability for the conduct of, or conditions caused by, others. We have not incurred, and do not expect to incur, material costs to comply with these laws and regulations.

        Our customers and collaborators are subject to substantial regulation by governmental agencies in the United States and other countries. Virtually all pharmaceutical products are subject to rigorous preclinical and clinical testing and other approval procedures by the FDA and by foreign regulatory agencies. Various federal and state laws and regulations also govern or influence the manufacturing, safety, labeling, storage, record keeping and marketing of these pharmaceutical products. This approval process is time-consuming and expensive, and there are no assurances that approval will be granted on a timely basis, or at all. Even if regulatory approvals are granted, a marketed product is subject to continual review.

        All facilities and manufacturing processes used in the production of Active Pharmaceutical Ingredients for clinical use in the United States must be operated in conformity with current good manufacturing practices (cGMP) as established by the FDA. We have completed construction of a cGMP manufacturing facility, which will allow us to produce cGMP compliant compounds for Phase I clinical testing. We have validated this capability for compliance with FDA regulations and began our first cGMP manufacturing campaign in the second half of calendar 2002. At this time, our cGMP facility is subject to periodic regulatory inspections to ensure compliance with cGMP requirements. We could also be required to comply with specific requirements or specifications of our collaborators, which may be more stringent than regulatory requirements. If we fail to comply with applicable regulations, the FDA could require us to cease ongoing research or disqualify the data submitted to regulatory authorities. A finding that we had materially violated cGMP requirements could result in additional regulatory sanctions and, in severe cases, could result in a mandated closing of our cGMP

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facility, which would materially and adversely affect our business, financial condition and results of operations.

        We are subject to other regulations, including regulations under the Occupational Safety and Health Act, regulations promulgated by the United States Department of Agriculture, and regulations under other federal, state and local laws.

Intellectual Property

        Our success will depend in part on our ability to protect our proprietary software, potential drug candidates and other intellectual property rights. To establish and protect our proprietary technologies and products, we rely on a combination of patent, copyright, trademark and trade secret laws, as well as confidentiality provisions in our contracts with collaborators.

        We attempt to protect our trade secrets by entering into confidentiality agreements with third parties, employees and consultants. Our employees also sign agreements requiring that they assign to us their interests in inventions, original expressions and any corresponding patents and copyrights arising from their work for us. However, it is possible that these agreements may be breached, invalidated or rendered unenforceable, and if so, we may not have an adequate remedy available. Despite the measures we have taken to protect our intellectual property, parties to our agreements may breach the confidentiality provisions or infringe or misappropriate our patents, copyrights, trademarks, trade secrets and other proprietary rights. In addition, third parties may independently discover or invent competing technologies or reverse-engineer our trade secrets or other technology.

        We have also implemented a patent strategy designed to protect technology, inventions and improvements to inventions that are commercially important to our business. We currently have six issued United States patents and ten patent applications on file with the United States Patent and Trademark Office. We have three international patent applications and 31 patent applications filed in foreign countries that correspond to U.S. patents or patent applications.

        United States patents issued from applications filed on or after June 8, 1995, have a term of 20 years from the application filing date or earlier claimed priority. All of our patent applications were filed after June 8, 1995. Patents in most other countries have a term of 20 years from the date of filing of the patent application. Because the time from filing patent applications to issuance of patents is often several years, this process may result in a period of patent protection significantly shorter than 20 years, which may adversely affect our ability to exclude competitors from our markets. Our success will depend in part upon our ability to develop proprietary products and technologies and to obtain patent coverage for these products and technologies. We intend to continue to file patent applications covering newly developed products and technologies. We may not, however, commercialize the technology underlying any or all of our existing or future patent applications.

        Patents provide some degree of protection for our proprietary technology. However, the pursuit and assertion of patent rights, particularly in areas like pharmaceuticals and biotechnology, involve complex legal and factual determinations and, therefore, are characterized by some uncertainty. In addition, the laws governing patentability and the scope of patent coverage continue to evolve, particularly in biotechnology. As a result, patents may not issue from any of our patent applications or from applications licensed to us. The scope of any of our patents, if issued, may not be sufficiently broad to offer meaningful protection. In addition, our patents or patents licensed to us, if they are issued, may be successfully challenged, invalidated, circumvented or rendered unenforceable so that our patent rights might not create an effective competitive barrier. Moreover, the laws of some foreign countries may not protect our proprietary rights to the same extent, as do the laws of the United States. Any patents issued to us or our strategic partners may not provide a legal basis for establishing an exclusive market for our products or provide us with any competitive advantages. Moreover, the patents held by others may adversely affect our ability to do business or to continue to use our

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technologies freely. In view of these factors, our intellectual property positions bear some degree of uncertainty.

        The source code for our proprietary software programs is protected both as a trade secret and as a copyrighted work.

Employees

        As of June 30, 2003, we had 244 full-time employees, including 183 scientists, of whom 106 have Ph.D.s and 74 have experience at large pharmaceutical or biotechnology companies. None of our employees are covered by collective bargaining agreements, and we consider our employee relations to be good.

Available Information

        We were incorporated in February 1998 under the name Array BioPharma Inc. Our principal executive offices are located at 3200 Walnut Street, Boulder, Colorado 80301, and our telephone number is (303) 381-6600. Our web site can be found at www.arraybiopharma.com. Information on our web site does not constitute any part of this Annual Report on Form 10-K. The annual reports on Form 10-K, quarterly reports on Form 10-Q, current reports on Form 8-K, and amendments to those reports, that we file with or furnish to the SEC are available on our web site free of charge as soon as reasonably practicable following the filing or furnishing of these reports with the SEC.

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Risk Factors

Risks Related to Our Business

WE MAY NOT ACHIEVE OR SUSTAIN PROFITABILITY.

        We are at an early stage of executing our business plan, and we have a limited history of offering our drug discovery capabilities. We have incurred operating and net losses and negative cash flows from operations since our inception. As of June 30, 2003, we had an accumulated deficit of $44.2 million. We had net losses of $19.6 million, $4.5 million and $10.6 million for the fiscal years ended June 30, 2003, 2002 and 2001, respectively. We may continue to incur operating and net losses and negative cash flows, due in part to anticipated increases in expenses for research and development, expansion of our scientific and business development capabilities, and acquisitions of complementary businesses and technologies. We may not be able to achieve or maintain profitability. Moreover, if we do achieve profitability, the level of any profitability cannot be predicted and may vary significantly from quarter to quarter.

OUR BUSINESS IS DEPENDENT UPON THE EXTENT TO WHICH THE PHARMACEUTICAL AND BIOTECHNOLOGY INDUSTRIES COLLABORATE WITH DRUG DISCOVERY COMPANIES FOR ONE OR MORE ASPECTS OF THEIR DRUG DISCOVERY PROCESS.

        We are highly dependent on pharmaceutical and biotechnology companies continuing to collaborate with outside companies to obtain drug discovery expertise and on their willingness to spend significant funds on research and development. Our capabilities include aspects of the drug discovery process that pharmaceutical and biotechnology companies have traditionally performed internally. The willingness of these companies to expand or continue drug discovery collaborations to enhance their research and development process is based on several factors that are beyond our control, such as their ability to hire and retain qualified scientists, the resources available for entering into drug discovery collaborations, the spending priorities among various types of research activities and their policies regarding the balance of research expenditures versus cost containment. Any of these factors could cause our revenue to decline. In addition, our ability to convince these companies to use our drug discovery capabilities, rather than develop them internally, will depend on many factors, including our ability to:

•

provide scientists and technologies that are of the highest caliber;



•

develop drug discovery technologies that will result in the identification of higher-quality drug candidates;



•

achieve intended results in a timely fashion, with acceptable quality and at an acceptable cost; and



•

design, create and manufacture sufficient quantities of our chemical compounds for our collaborators.

        The importance of these factors varies from company to company, and although we believe we currently address them for our collaborators, we may be unable to meet any or all of them for some of our collaborators in the future. Even if we are able to address these factors, these companies may still decide to perform these activities internally or with other companies that provide drug research and development expertise similar to ours.

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BECAUSE WE RELY ON A SMALL NUMBER OF COLLABORATORS FOR A SIGNIFICANT PORTION OF OUR REVENUE, IF ONE OR MORE OF OUR MAJOR COLLABORATORS TERMINATES OR REDUCES THE SCOPE OF THEIR AGREEMENT WITH US, OUR REVENUE MAY SIGNIFICANTLY DECREASE AND OUR RESULTS OF OPERATIONS MAY BE HARMED.

        A relatively small number of collaborators account for a significant portion of our revenue. During the fiscal year ended June 30, 2003, revenue from, ICOS Corporation, Merck & Co., Inc. and Eli Lilly and Company accounted for 21%, 15% and 12%, respectively, of our total revenue. One of our agreements with Merck is terminable upon payment of a termination fee and otherwise expires in December 2003; our agreements with ICOS were completed in July and August 2003, and only a portion of one of them was renewed; our agreement with Eli Lilly terminates in March 2005, or earlier upon payment of a termination fee. We expect that revenue from a limited number of collaborators will account for a large portion of our revenue in future quarters. In general, our collaborators may terminate their contracts with us upon 30 to 90 days' notice for a number of reasons or, in some cases, for no reason. In addition, some of our major collaborators can determine the amount of products delivered and research or development performed under these agreements. As a result, if any one of our major collaborators cancels, declines to renew or reduces the scope of its contract with us, our revenue may decrease.

WE MAY FAIL TO EXPAND COLLABORATOR RELATIONSHIPS.

        One of our business strategies is to continue to expand our existing collaborator relationships across the full spectrum of the Array Discovery Platform. The number of large pharmaceutical and biotechnology companies that could potentially use our capabilities is limited. As a result, we must expand our existing collaborator relationships in order to maximize our potential revenue. However, we may not be able to expand these existing relationships. We have worked with over 200 companies; approximately 10% of these companies have chosen to expand their relationship to access additional capabilities of the Array Discovery Platform.

WE MAY NOT SUCCESSFULLY DEVELOP A DRUG CANDIDATE THAT BECOMES A COMMERCIALLY AVAILABLE DRUG OR ENTER INTO ADDITIONAL COLLABORATIONS THAT ALLOW US TO PARTICIPATE IN THE FUTURE SUCCESS OF OUR PROPRIETARY DRUG CANDIDATES THROUGH MILESTONE, ROYALTY AND/OR LICENSE PAYMENTS.

        We have committed, and intend to continue to commit, significant resources to create our own proprietary drug candidates and collaborate with a partner for co-development and commercialization, allowing us to earn upfront, license, research funding, milestone and/or royalty payments. In fiscal 2003, we increased our investment in proprietary research to $11.2 million compared to $5.5 million for fiscal 2002. Our proprietary drug discovery program is in its early stage of development and unproven. We have received limited license fees, one milestone payment and limited royalties to date. Although we have expended, and continue to expend, time and money on internal research and development for our proprietary programs and for our collaborators, we may not be successful in creating valuable proprietary drug candidates that would enable us to form additional collaborations and receive additional milestone, royalty and/or license payments. Moreover, our strategy is dependent on biotechnology and pharmaceutical companies continuing to license drug candidates to fill their product pipelines. Even if we are able to negotiate additional collaborations, the drug discovery process is highly uncertain and we have not discovered, and may never discover drug candidates that ultimately lead to a commercially viable drug. Product candidates that appear promising in the early phases of development may fail to become commercially viable drugs for a number of reasons, including: clinical trial results that indicate a candidate is not effective in treating a specified condition or illness in humans or has harmful side effects; the failure to obtain FDA or other regulatory approval; the assessment of our collaborators as to the commercial viability of manufacturing a particular drug; the

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intellectual property rights to a drug candidate that we or our collaborators cannot acquire on reasonable terms; and existing therapeutics that are more effective or economical to produce.

WE MAY NOT BE ABLE TO OFFER CERTAIN OF OUR RESEARCH TOOLS OR SERVICES THAT MEET THE REQUIREMENTS OF OUR COLLABORATORS OR OFFER THEM AT A COMPETITIVE PRICE.

        Requirements for research tools and services, such as Optimer Building Blocks, Lead Generation Libraries or custom synthesis, vary from collaborator to collaborator. We may be unable to meet these requirements for some of our collaborators. Other companies may offer research tools and services that more closely meet our collaborators' requirements, or our collaborators may decide to fulfill some or all of their needs internally. In addition, domestic and international competition may increase, and as a result, we may not be price competitive for certain of our research tools and services. Foreign competitors may have significantly lower cost structures, primarily resulting from lower scientific salaries.

WE MAY NOT BE ABLE TO RECRUIT AND RETAIN THE EXPERIENCED SCIENTISTS AND MANAGEMENT WE NEED TO COMPETE IN THE DRUG RESEARCH AND DEVELOPMENT INDUSTRY.

        We have 244 full-time employees as of June 30, 2003, and our future success depends upon our ability to attract, retain and motivate highly skilled scientists and management. Our ability to attract new collaborators and retain, renew and expand existing collaborations depends on our ability to hire and retain scientists with the skills necessary to provide appropriate drug discovery expertise. We compete with pharmaceutical and biotechnology companies, including our collaborators, medicinal chemistry outsourcing companies, contract research companies and academic and research institutions to recruit scientists. We may not be successful in attracting new scientists or management or in retaining or motivating our existing personnel.

        Our future success also depends on the personal efforts and abilities of the principal members of our senior management and scientific staff to provide strategic direction, manage our operations and maintain a cohesive and stable environment. In particular, we rely on the services of Robert E. Conway, our Chief Executive Officer; Dr. Kevin Koch, our President and Chief Scientific Officer; Dr. David L. Snitman, our Chief Operating Officer and Vice President, Business Development; Dr. Anthony D. Piscopio, our Vice President, Chemistry and Director of Process Chemistry; R. Michael Carruthers, our Chief Financial Officer; and John R. Moore, our Vice President and General Counsel. We have employment agreements with all of the above personnel that are terminable upon 30 days' prior notice. If we cannot attract and retain qualified scientists and management, we will not be able to continue to provide or expand our drug discovery offerings.

WE MAY NOT BE ABLE TO ACCELERATE THE DRUG DISCOVERY PROCESS.

        One of our business strategies is to accelerate the drug discovery process to identify drug candidates using the Array Discovery Platform. It is uncertain whether we will be able to make the drug discovery process more efficient or create higher-quality drug candidates. Our ability to accelerate the drug discovery process depends on many factors, including the implementation of appropriate technologies, the development of effective new research tools and the performance and decision-making capabilities of our scientists. Our information-driven technology platform, which we believe allows our scientists to make better decisions, may not enable our scientists to make correct decisions or develop viable drug candidates.

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WE MAY NOT BE ABLE TO MEET THE DELIVERY AND PERFORMANCE REQUIREMENTS SET FORTH IN OUR COLLABORATION AGREEMENTS.

        In order to maintain our current collaborative relationships and to meet the performance and delivery requirements in our agreements, we must be able to provide drug discovery capabilities at appropriate levels, with acceptable quality and at an acceptable cost. Our ability to deliver the drug discovery capabilities we offer to our collaborators is limited by many factors, including the difficulty of the chemistry and biology, the lack of predictability in the scientific process and having adequate scientific expertise. In particular, a significant portion of our revenue depends on producing collections of chemical compounds, which requires a high rate of production. The inability to increase or maintain our current rate of compound synthesis to meet our existing or future contractual commitments may result in delayed or lost revenue, loss of collaborators or failure to expand our existing relationships.

OUR QUARTERLY OPERATING RESULTS COULD FLUCTUATE SIGNIFICANTLY.

        Sales of our drug discovery capabilities, including our Lead Generation Libraries, typically involve significant technical evaluation and/or commitment of capital by our collaborators. Accordingly, the sales cycles are lengthy and subject to a number of significant risks, including collaborators' budgetary constraints and internal acceptance reviews. In addition, some of our collaborators can influence when we deliver products and perform services under their contracts with us. Due to these factors, our operating results could fluctuate significantly from quarter to quarter. In addition, we may experience significant fluctuations in quarterly operating results due to factors such as general and industry-specific economic conditions that may affect the research and development expenditures of pharmaceutical and biotechnology companies.

        Due to the possibility of fluctuations in our revenue and expenses, we believe that quarter-to-quarter comparisons of our operating results are not a good indication of our future performance. Our operating results in some quarters may not meet the expectations of stock market analysts and investors. If we do not meet analysts' and/or investors' expectations, our stock price could decline.

WE MAY NOT OBTAIN REGULATORY APPROVAL FOR THE SALE AND MANUFACTURE OF DRUG CANDIDATES THAT WE DEVELOP WITH OUR COLLABORATORS OR ON OUR OWN.

        The development and commercialization of drug candidates for our collaborators and our own internal drug discovery efforts are subject to regulation. Pharmaceutical products require lengthy and costly testing in animals and humans and regulatory approval by governmental agencies prior to commercialization. Approval of a drug candidate as safe and effective for use in humans is never certain and these agencies may delay or deny approval of the products for commercialization despite the substantial time and resources required to obtain approvals and to comply with appropriate statutes and regulations. Regulatory agencies may also delay or deny approval based on additional government regulation or administrative action or on changes in regulatory policy during the period of clinical trials in humans and regulatory review. Similar delays and denials may be encountered in foreign countries. None of our collaborators have obtained regulatory approval to manufacture and sell drug candidates owned by us or identified and/or developed under an agreement with us. If we and/or our collaborators cannot obtain this approval, we may not realize milestone or royalty payments based on commercialization goals for these drug candidates. Even if regulatory approval is obtained, clinical studies may be required after sales of a drug have begun. In addition, the identification of certain side effects after a drug is on the market may result in the subsequent withdrawal of approval, reformulation of a drug, additional preclinical and clinical trials and changes in labeling. Any of these events could delay or prevent us from generating revenue from the commercialization of these drugs.

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OUR cGMP AND PHARMACOLOGY FACILITIES AND PRACTICES MAY FAIL TO COMPLY WITH GOVERNMENT REGULATIONS.

        All facilities and manufacturing processes used in the production of Active Pharmaceutical Ingredients for clinical use in the United States must be operated in conformity with current good manufacturing practices, or cGMP, as established by the FDA. Our cGMP facility and practices are subject to periodic regulatory inspections to ensure compliance with cGMP requirements. In addition, we could be required to comply with specific requirements of our collaborators, which may exceed FDA requirements. Failure on our part to comply with applicable regulations and specific requirements of our collaborators could result in the termination of ongoing research or the disqualification of data for submission to regulatory authorities. A finding that we had materially violated cGMP requirements could result in additional regulatory sanctions and, in severe cases, could result in a mandated closing of our cGMP facility.

        In addition, our pharmacology facility may be subject to the United States Department of Agriculture (USDA) regulations for certain animal species. Failure on our part to comply with applicable regulations and specific requirements of our collaborators could result in the termination of ongoing pharmacology research. A finding that we had materially violated USDA requirements could result in additional regulatory sanctions and, in severe cases, could result in a mandated closing of our pharmacology facility for certain species.

OUR DEVELOPMENT, TESTING AND MANUFACTURE OF POTENTIAL DRUG CANDIDATES MAY EXPOSE US TO PRODUCT LIABILITY LAWSUITS.

        We develop, test and manufacture the precursors to therapeutic drugs generally intended for use in humans. Our drug discovery activities that result in the future manufacture and sale of drugs by our collaborators expose us to the risk of liability for personal injury or death to persons using these drugs. We may be required to pay substantial damages or incur legal costs in connection with defending any of these product liability claims, or we may not receive revenue from expected royalty or milestone payments if the commercialization of a drug is limited or ceases as a result of such claims. We have product liability insurance that contains customary exclusions and provides coverage up to $2.0 million per occurrence and in the aggregate, which we believe is customary in our industry. However, our product liability insurance does not cover every type of product liability claim that we may face or loss we may incur, and may not adequately compensate us for the entire amount of covered claims or losses or for the harm to our business reputation. We may be unable to acquire or maintain additional or maintain our current insurance policies at acceptable costs or at all.

IF OUR USE OF CHEMICAL AND HAZARDOUS MATERIALS VIOLATES APPLICABLE LAWS OR REGULATIONS OR CAUSES PERSONAL INJURY WE MAY BE LIABLE FOR DAMAGES.

        Our drug discovery activities, including the analysis and synthesis of chemical compounds, involve the controlled use of chemicals, including flammable, combustible, toxic and radioactive materials that are potentially hazardous. Our use, storage, handling and disposal of these materials is subject to federal, state and local laws and regulations, including the Resource Conservation and Recovery Act, the Occupational Safety and Health Act and local fire codes, and regulations promulgated by the Department of Transportation, the Drug Enforcement Agency, the Department of Energy, the Colorado Department of Public Health and Environment, and the Colorado Department of Human Services, Alcohol and Drug Abuse Division. We may incur significant costs to comply with these laws and regulations in the future. In addition, we cannot completely eliminate the risk of accidental contamination or injury from these materials. In the event of such an accident, we could be liable for any damages that result, and any such liability could exceed our resources and disrupt our business.

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OUR OPERATIONS COULD BE INTERRUPTED BY DAMAGE TO OUR SPECIALIZED LABORATORY FACILITIES.

        Our operations are dependent upon the continued use of our highly specialized laboratories and equipment in Boulder and Longmont, Colorado. Catastrophic events, including fires or explosions, could damage our laboratories, equipment or inventories of chemical compounds and may materially interrupt our business. We employ safety precautions in our laboratory activities in order to reduce the likelihood of the occurrence of these catastrophic events; however, we cannot eliminate the chance that such an event will occur. The availability of laboratory space in these areas is extremely limited, and rebuilding our facilities could be time consuming and result in substantial delays in fulfilling our agreements with our collaborators. We maintain business interruption insurance in the amount of $12.0 million to cover continuing expenses and lost revenue caused by such occurrences. However, this insurance would not compensate us for the loss of opportunity and potential harm to customer relations that our inability to meet our collaborators' needs in a timely manner could create.

Risks Related to Operating in Our Industry

THE CONCENTRATION OF THE PHARMACEUTICAL INDUSTRY AND ANY FURTHER CONSOLIDATION COULD REDUCE THE NUMBER OF OUR POTENTIAL COLLABORATORS.

        There are a limited number of large pharmaceutical companies, and these companies represent a significant portion of the market for our capabilities. The number of our potential collaborators could decline even further through consolidation among these companies. If the number of our potential collaborators declines even further, they may be able to negotiate price discounts or other terms that are unfavorable to us.

CAPITAL MARKET CONDITIONS MAY REDUCE OUR BIOTECHNOLOGY COLLABORATORS' ABILITY TO FUND RESEARCH.

        Traditionally, many unprofitable biotechnology companies have funded their research and development expenditures through raising capital in the equity markets. Declines in these markets have severely restricted raising new capital in the past three years and have affected these companies' ability to continue to expand or fund existing research and development efforts. If our current or future biotechnology collaborators are unable to raise sufficient capital to fund research and development expenditures, we may not be able to expand or maintain current revenues.

HEALTH CARE REFORM COULD REDUCE THE PRICES PHARMACEUTICAL AND BIOTECHNOLOGY COMPANIES CAN CHARGE FOR DRUGS THEY SELL WHICH, IN TURN, COULD REDUCE THE AMOUNTS THAT THEY HAVE AVAILABLE TO RETAIN OUR SERVICES.

        We generate a majority of our revenues from contracts with pharmaceutical and biotechnology companies. We therefore depend upon the ability of pharmaceutical and biotechnology companies to earn profits on the drugs they market to devote substantial resources to the research and development of new drugs. Future legislation may limit the prices pharmaceutical and biotechnology companies can charge for the drugs they market. Such laws may have the effect of reducing the resources that pharmaceutical and biotechnology companies can devote to the research and development of new drugs, which could reduce the amount of services that we perform and our resulting revenues.

THE DRUG RESEARCH AND DEVELOPMENT INDUSTRY HAS A HISTORY OF PATENT AND OTHER INTELLECTUAL PROPERTY LITIGATION, AND WE MAY BE INVOLVED IN COSTLY INTELLECTUAL PROPERTY LAWSUITS.

        The drug research and development industry has a history of patent and other intellectual property litigation, and we believe these lawsuits are likely to continue. Because we produce and provide many

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different capabilities in this industry, we face potential patent infringement suits by companies that control patents for similar capabilities or other suits alleging infringement of their intellectual property rights. In order to protect or enforce our intellectual property rights, we may have to initiate legal proceedings against third parties. Legal proceedings relating to intellectual property would be expensive, take significant time and divert management's attention from other business concerns, whether we win or lose. Further, if we do not prevail in an infringement lawsuit brought against us, we might have to pay substantial damages, including triple damages, and we could be required to stop the infringing activity or obtain a license to use the patented technology.

THE INTELLECTUAL PROPERTY RIGHTS WE RELY ON TO PROTECT THE TECHNOLOGY UNDERLYING OUR TOOLS AND TECHNIQUES MAY BE INADEQUATE TO PREVENT THIRD PARTIES FROM USING OUR TECHNOLOGY OR DEVELOPING COMPETING CAPABILITIES OR TO PROTECT OUR INTERESTS IN OUR PROPRIETARY DRUG CANDIDATES.

        Our success will depend in part on our ability to protect patents or maintain the secrecy of proprietary processes and other technologies we develop for the testing and synthesis of chemical compounds in the drug discovery process. In addition, one of our business strategies is to develop our own proprietary drug candidates and enter into collaborations with pharmaceutical and biotechnology companies for the development of these drug candidates. In order to protect our rights to our proprietary drug candidates, we must obtain and maintain the intellectual property rights to such drug candidates. We currently have six issued United States patents and ten patent applications on file with the United States Patent and Trademark Office. We have three international patent applications and 31 patent applications filed in foreign countries that correspond to U.S. patents or patent applications. Any patents that we may own or license now or in the future may not afford meaningful protection for our technology and tools. Our efforts to enforce and maintain our intellectual property rights may not be successful and may result in substantial costs and diversion of management time. In addition, other companies may challenge our patents and, as a result, these patents could be narrowed, invalidated or rendered unenforceable, or we may be forced to stop using the technology covered by these patents or to license the technology from third parties. In addition, current and future patent applications on which we depend may not result in the issuance of patents in the United States or foreign countries. Even if our rights are valid, enforceable and broad in scope, competitors may develop products based on similar technology that is not covered by our patents.

        In addition to patent protection, we also rely on copyright and trademark protection, trade secrets, know-how, continuing technological innovation and licensing opportunities. In an effort to maintain the confidentiality and ownership of our trade secrets and proprietary information, we require our employees, consultants and advisors to execute confidentiality and proprietary information agreements. However, these agreements may not provide us with adequate protection against improper use or disclosure of confidential information and there may not be adequate remedies in the event of unauthorized use or disclosure. Furthermore, we may from time to time hire scientific personnel formerly employed by other companies involved in one or more areas similar to the activities we conduct. In some situations, our confidentiality and proprietary information agreements may conflict with, or be subject to, the rights of third parties with whom our employees, consultants or advisors have prior employment or consulting relationships. Although we require our employees and consultants to maintain the confidentiality of all proprietary information of their previous employers, these individuals, or we, may be subject to allegations of trade secret misappropriation or other similar claims as a result of their prior affiliations. Finally, others may independently develop substantially equivalent proprietary information and techniques or otherwise gain access to our trade secrets. Our failure to protect our proprietary information and techniques may inhibit or limit our ability to exclude certain competitors from the market.

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THE DRUG RESEARCH AND DEVELOPMENT INDUSTRY IS HIGHLY COMPETITIVE, AND WE COMPETE WITH SOME COMPANIES THAT OFFER A BROADER RANGE OF CAPABILITIES AND HAVE BETTER ACCESS TO RESOURCES THAN WE DO.