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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

FORM 10-K

For the Fiscal Year Ended December 31, 2003

SANGAMO BIOSCIENCES, INC.
(Exact name of registrant as specified in its charter)

501 Canal Boulevard, Suite A100
Richmond, CA 94804
(510) 970-6000
(Address, including zip code, and telephone number, including area code,
of the registrant's principal executive offices)

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

Securities registered pursuant to Section 12(g) of the act:

Common stock $.01 par value
(Title of Class)

        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 (Section 229.405 of this chapter) 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.    o

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

        The aggregate market value of the voting stock held by non-affiliates of the Registrant on June 30, 2003, based on the closing sale price as reported by the Nasdaq National Market of the Company's Common Stock, was approximately $50,955,969.

        The total number of shares outstanding of the Registrant's Common Stock was 24,975,003 as of February 18, 2004.

DOCUMENTS INCORPORATED BY REFERENCE

        Portions of the Registrant's Proxy Statement for its 2004 Annual Meeting of Stockholders (the "2004 Proxy Statement") are incorporated by reference into Part III of this Form 10-K.

TABLE OF CONTENTS

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

        Some statements contained in this report are forward-looking with respect to our operations, economic performance and financial condition. Statements that are forward-looking in nature should be read with caution because they involve risks and uncertainties, which are included, for example, in specific and general discussions about:

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our strategy;



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sufficiency of our cash resources;



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product development;



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revenues from existing and new collaborations;



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our research and development and other expenses;



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our operational and legal risks; and



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our plans, objectives, expectations and intentions and any other statements that are not historical facts.

        Various terms and expressions similar to them are intended to identify these cautionary statements. These terms include: "anticipates," "believes," "continues," "could," "estimates," "expects," "intends," "may," "plans," "seeks," "should" and "will." Actual results may differ materially from those expressed or implied in those statements. Factors that could cause these differences include, but are not limited to, those discussed under "Risk Factors" and "Management's Discussion and Analysis of Financial Condition and Results of Operations." Sangamo undertakes no obligation to publicly release any revisions to forward-looking statements to reflect events or circumstances arising after the date of this report. Readers are cautioned not to place undue reliance on the forward-looking statements, which speak only as of the date of this Annual Report on Form 10-K.

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PART I

Item 1.    Business

Company Overview and Business Strategy

Background

        Sangamo is the worldwide leader in the research, development, and commercialization of DNA binding proteins for the targeted regulation of gene expression and targeted gene correction. Our proprietary technology platform is based on the engineering of a naturally occurring class of proteins referred to as zinc finger DNA binding proteins (ZFPs). We believe that the DNA binding domain of ZFPs can be targeted to virtually any gene in the human genome or any other eukaryotic cell genome. Our scientists use engineered ZFPs to make ZFP transcription factors, or ZFP TFs, that are able to turn genes on or off (see Figure A). Alternatively, ZFPs may be modified with nuclease functional domains to create zinc finger nucleases (ZFNs). These engineered ZFNs can precisely cut genomic DNA at a preselected location, facilitating the transfer of "corrected" or "donor" genetic information into the site and thus allowing the "repair" or "correction" of specific genes carrying disease-causing mutations.

        Pharmaceutical companies have spent billions of dollars to successfully discover and validate new genomic targets over the last several years, yet they have failed, in many cases, to identify small-molecule drugs which can therapeutically modulate these targets in man. We believe that our ZFP technology platform constitutes a novel therapeutic approach enabling the regulation of validated drug targets which have proven intractable to conventional methods of drug discovery. Sangamo, by offering ZFP TF regulation or correction of such targets at the DNA level, is poised to address such high-value targets by providing a unique and proprietary approach to the therapeutic regulation or correction of disease-associated genes. Our corporate partner, Edwards Lifesciences (Edwards), has filed an investigational new drug (IND) application to initiate a Phase I/II clinical study, which is intended to evaluate the safety and preliminary efficacy of a proprietary Sangamo ZFP Therapeutic™ for the treatment of peripheral artery disease (PAD). We have also initiated preclinical animal studies of ZFP Therapeutics in diabetic neuropathy and congestive heart failure and have research-stage programs in neuropathic pain, cancer immunotherapy, X-linked severe combined immunodeficiency (X-linked SCID), and sickle cell anemia.

        Going forward, we intend to invest the majority of our financial and scientific resources in therapeutic applications of our ZFP technology. Notwithstanding our therapeutic focus, we believe the potential commercial applications of ZFP TFs are broad-based and range from human therapeutics and drug discovery to protein pharmaceutical production and the precision engineering of commercial crop plants. Our business model permits us to capitalize on the ZFP platform by permitting the sale or licensing of ZFP TFs or ZFNs to companies working in any of these fields. For instance, Sangamo has supplied its pharmaceutical partners with ZFP TFs for the engineering of human cells to enable their use in compound screening against cell surface receptors that are high-value drug targets. In addition, we are supplying Medarex, Inc. with ZFP-engineered cells for the enhanced production and yield of therapeutic antibodies, an advance which could substantially increase the efficiency of Medarex's pharmaceutical antibody production. Finally, while Sangamo is not currently investing in plant agriculture projects, our ZFP technology has been demonstrated to enable precise changes in the genomes of crop plants for commercially desirable traits.

        We have amassed a substantial proprietary position in the design, selection, composition, and use of engineered ZFPs to support all of these commercial products. We either own outright or have licensed the commercial rights to approximately 42 patents issued in the United States and foreign national jurisdictions, and we have over 175 patent applications pending worldwide. We continue to license and file new patent applications that strengthen our core and accessory patent portfolio. We

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believe that our proprietary position will protect our ability to research, develop, and commercialize products and services based on ZFP technology across all of our chosen applications.

        Over the last 18 months, we have increasingly focused our company on ZFP Therapeutic product development and recruited experienced scientists and managers with substantial product development experience. Working with the Edwards Lifesciences development team, we have played an integral role in the filing of the IND application. We are also building our capabilities in preclinical development, regulatory affairs, manufacturing, and clinical research and are applying these capabilities across our product development programs in cardiovascular disease, neurological disorders, cancer immunotherapy, and the treatment of monogenic diseases, including X-linked SCID and sickle cell anemia.

DNA, Genes, and Transcription Factors

        DNA is present in all cells and encodes the inherited characteristics of all living organisms. A cell's DNA is organized in chromosomes as thousands of individual units called genes. Genes encode proteins, which are assembled through the process of transcription—whereby DNA is transcribed into ribonucleic acid, (RNA)—and, subsequently, translation—whereby RNA is translated into protein. DNA, RNA, and proteins comprise many of the targets for pharmaceutical drug discovery and therapeutic intervention at the molecular level.

        The human body is composed of specialized cells that perform different functions and are thus organized into tissues and organs. All cells in an individual's body contain the same set of genes. However, only a fraction of these genes are turned on, or expressed, in an individual human cell at any given time. Genes are activated or repressed in response to a wide variety of stimuli (external factors) and developmental signals (internal factors). Distinct sets of genes are expressed in different cell types. It is this pattern of gene expression that determines the structure, biological function, and health of all cells, tissues, and organisms. The aberrant expression of certain genes can lead to disease.

        Transcription factors are proteins that bind to genes and regulate their expression. A transcription factor recognizes and binds to a specific DNA sequence within or near a particular gene and causes that gene to be activated or repressed. In higher organisms, transcription factors typically comprise two principal domains: the first is a DNA binding domain, which recognizes a target DNA sequence and thereby directs the transcription factor to the proper chromosomal location; the second is a functional domain that causes the target gene to be activated or repressed (see Figure A). The two-component structure of our engineered ZFP TFs is modeled on this naturally occurring structure of transcription factors in all higher organisms.

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The Two Domain Structure of a ZFP Therapeutic

Figure A

Engineered Zinc Finger Protein Transcription Factors (ZFP TFs) for Therapeutic Gene Regulation

        Consistent with the two-domain structure of ZFP TFs, we take a modular approach to their design. The recognition domain is typically composed of three or more zinc fingers; each finger recognizes and binds to a three base pair sequence of DNA, and multiple fingers can be linked together to recognize longer stretches of DNA. By modifying the amino acids of a ZFP that directly interact with DNA, we can engineer novel ZFPs capable of recognizing preselected DNA sequences within genes of commercial interest.

        The ZFP DNA binding domain is coupled to a functional domain, creating a ZFP TF capable of controlling or regulating a target gene in the desired manner. For instance, an activation domain causes a target gene to be "turned on." Alternatively, a repression domain causes the gene to be "turned off." We believe that we can control the duration of the effects of ZFP TFs by several methods. ZFP TFs may be delivered by using different gene transfer systems that allow them to be expressed in a cell transiently or continuously. We can also engineer ZFP TFs with functional domains that allow their activity to be controlled by the administration of a small-molecule drug. Finally, we can engineer ZFP TFs with repression domains that are able to inhibit gene expression and, in some cases, even silence their target genes.

        To date, we have designed, engineered, and assembled several thousand ZFPs and have thoroughly tested the majority of these proteins for their affinity, or tightness of binding to their DNA target, as well as their specificity, or preference for their intended DNA target. We have developed standardized methods for the design, selection, and assembly of ZFPs capable of binding to a wide spectrum of DNA sequences and genes. We have linked ZFPs to numerous functional domains to create gene-specific ZFP TFs and have demonstrated the ability of these ZFP TFs to regulate hundreds of genes in dozens of different cell types and directly in whole organisms, including mice, rats, rabbits,

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pigs, plants, fruit flies, worms, and yeast. Sangamo scientists have published extensively, in peer-reviewed scientific journals, on the transcriptional function of ZFP TFs and the resulting changes in the behavior of the target cell, tissue, or organism.

Engineered ZFNs for Therapeutic Gene Correction

        The ZFP DNA binding domain may also be coupled to a cleavage domain of a restriction endonuclease—an enzyme that cuts DNA at a precise location. Using the DNA binding domain of an engineered ZFP, we can design a ZFN to generate a physical break at a defined position in the DNA sequence of a target gene that carries a disease-causing mutation. This targeted break in the DNA facilitates the replacement of the disease-causing mutation or DNA sequence with the "normal" or "corrected" DNA sequence. We believe that ZFN-mediated gene correction will allow the corrected gene to be expressed in its natural chromosomal context and may provide a safe and effective approach to the precise repair of DNA sequence mutations responsible for monogenic diseases such as X-linked SCID and sickle cell anemia.

A Novel Class of Human Therapeutics

        With our ability to deliver gene-specific ZFP TFs and ZFNs for the activation, repression, silencing, or repair of target genes and DNA sequences, we are poised to develop a novel class of highly differentiated human therapeutics. We believe that, as more genes are validated as high-value therapeutic targets, the clinical breadth and scope of ZFP Therapeutic applications may prove to be substantial.

        Following the genomics revolution of the 1990s, the sequencing and publication of the human genome, and the industrialization of genomics-based drug discovery in this decade, pharmaceutical and biotechnology companies have validated and characterized hundreds of new drug targets. However, these companies have had mixed results in translating these targets into lead product candidates, or products which have advanced to clinical trials. There are thousands of potential drug targets which, although they have a clear role in disease processes, cannot be bound or modulated by small molecules with drug-like properties. Alternative therapeutic approaches may be required to modulate the biological activity of these so-called "non-druggable" targets. This may create a significant clinical and commercial opportunity for the therapeutic regulation of disease-associated genes with engineered ZFP transcription factors.

        ZFP Therapeutics provide a unique approach to non-druggable targets. ZFP TFs act through a mechanism that is unique among biological drugs: direct modulation of the "disease" gene as opposed to the protein target encoded by that gene. Thus, a protein target which may be intractable to compound screening can instead be "turned on" or "turned off" at the DNA level. Engineered ZFP TFs are the only class of therapeutic molecules which act directly through the regulation of gene expression. This mode of action is not available to conventional small molecules, antibodies, or other protein pharmaceuticals.

        Therefore, we believe that ZFP Therapeutics provide a unique and proprietary approach to therapeutic design and have significant competitive advantages over small-molecule drugs, protein pharmaceuticals, and conventional gene therapy:

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ZFP Therapeutics act at the DNA level to regulate gene expression, allowing direct modulation of the gene or target;



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ZFP Therapeutics circumvent the "non-druggable" properties of many drug targets;



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ZFP TFs can either activate or repress therapeutic gene targets;



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ZFP TFs can activate the expression of all splice variants encoded by a particular gene;

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ZFP TFs may themselves be expressed either transiently, for acute indications, or longer term, for chronic conditions;



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ZFP TFs may ultimately be controllable by orally available small molecules for finer control of the intended gene target.

ZFP Therapeutic Gene Correction of Monogenic Disease

        Genetic diseases such as X-linked SCID, sickle cell anemia, and Gaucher's disease are caused by deleterious DNA sequence mutations within single genes. "Gene correction" is the process by which a mutation, or disease-causing DNA sequence, can be repaired by its replacement with the "correct" DNA sequence, restoring normal gene function. As mentioned above, our engineered ZFPs can be attached to nuclease domains to create ZFNs. The ZFN is able to "recognize" its intended gene target through its engineered (ZFP) DNA binding domain (Figure A). However, instead of regulating the expression of the target gene (as with a ZFP TF), the ZFN causes the gene to be cut near the ZFP binding site, facilitating the incorporation of the corrected DNA sequence into the chromosomal location where the disease-related mutation previously existed.

        While gene correction has been pursued in academic research laboratories for over a decade, its clinical application has been prevented by the low efficiency of homologous recombination (HR), the biological process of gene replacement. Unaided by an engineered ZFN, HR will only occur at a rate of approximately once in every one million cells; this rate is too low to be of clinical use. However, we and our collaborators have shown that the use of an engineered ZFN to cleave the target gene near the defective sequence can increase the efficiency of targeted HR by several thousand-fold. ZFP Therapeutic gene correction is a revolutionary technical approach to gene repair because ZFNs, like all ZFPs, can be engineered to recognize virtually any target gene in the human genome. We are working to generate the preclinical data necessary to evaluate the potential utility of this approach for X-linked SCID and sickle cell anemia.

THERAPEUTIC PRODUCT DEVELOPMENT

Product Development Strategy

        Over the last several years, we have shown that ZFP TFs can be engineered to bind their target genes with an optimal level of affinity and specificity and can regulate these targets in a way that causes the desired effect at the levels of target cell, tissue, and organism. We have extended these results to preclinical animal models of disease, including mice, rats, rabbits, and pigs. We have published some of these data in peer-reviewed journals, and our partner, Edwards Lifesciences, submitted these data to the United States Food & Drug Administration (FDA) along with preclinical toxicology and biodistribution data as part of an IND application. This IND application was filed on February 10, 2004 to support a Phase I/II clinical study to investigate the safety and preliminary efficacy of ZFP TFs designed to up-regulate the expression of vascular endothelial growth factor A (VEGF-A) in patients with PAD. The study will be conducted under the supervision of Robert J. Lederman, M.D. of the National Heart, Lung and Blood Institute, National Institutes of Health (NIH). We intend to develop the necessary preclinical data to support the filing of additional INDs for the clinical testing of ZFP Therapeutics in patients with cardiovascular disease, neurological disorders, cancer, and monogenic diseases including X-linked SCID and sickle cell anemia.

Product Development Programs

        In addition to the IND application to initiate the Phase I/II PAD clinical trial, we currently have three preclinical-stage programs (i.e., lead ZFP TF molecules in animal efficacy studies) and five

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research-stage programs (i.e., cell-based testing to identify and optimize lead ZFP TF or ZFN molecules for testing in animals).

Table 1.    Clinical indications currently targeted by Sangamo's clinical, preclinical, and research-stage product development programs.

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Peripheral Artery Disease (PAD)

        PAD is the result of inadequate arterial blood flow to the lower extremities. It is seen as a spectrum of disease, beginning with asymptomatic reduction in blood flow to the leg; followed by the development of intermittent claudication, which limits walking distance; followed by pain in the absence of exercise; and finally leading to tissue damage and severely impaired mobility. While the condition affects 8-12 million people in the United States, 80% of these patients have intermittent claudication and do not progress to resting pain or critical limb ischemia. This program is funded and managed by our development partner, Edwards Lifesciences, who filed an IND application in February 2004 to initiate a Phase I/II clinical trial in PAD.

Diabetic Neuropathy

        Diabetic neuropathy is a frequent complication of diabetes. Left unchecked, diabetic neuropathy can lead to impaired sensation in the feet, which can result in undiscovered soft tissue damage, infection, and, ultimately, amputation of the lower extremity. The most common form of diabetic neuropathy affects approximately 50% of patients with diabetes, or roughly six million people in the United States. In 2001, there were approximately 82,000 non-traumatic lower-limb amputations performed on diabetics in the United States. There are no pharmaceutical therapies approved by the FDA for the treatment of diabetic neuropathy. Administration of recombinant VEGF-A or the cDNA encoding VEGF-A has been observed to retard or partially reverse the condition in preclinical animal models of diabetic neuropathy. We have initiated preclinical studies of VEGF-A activation in similar preclinical models to confirm and extend these findings by using our ZFP Therapeutic to up-regulate the chromosomal VEGF-A gene.

Congestive Heart Failure (CHF)

        CHF is a gradual and long-term loss of pumping capacity by the heart that results in the "backing up" of blood and fluid (edema) in the lungs and other tissues and organs. This fluid congestion can cause shortness of breath, coughing, swelling of the abdomen and extremities, fatigue, kidney damage, and kidney failure. The incidence and prevalence of CHF are increasing at an alarming rate, with approximately 550,000 new cases in the United States each year and a current patient population of more than 5 million Americans. There is now strong scientific evidence to suggest that down-regulation of the gene encoding phospholamban (PLN) can improve the contractility of heart muscle in mammalian animal models of CHF. We have identified a lead ZFP TF inhibitor of PLN for the CHF program and have initiated preclinical studies in a rodent model of CHF.

Ischemic Heart Disease (IHD)

        Ischemic heart disease results from inadequate blood flow to the heart. The most common manifestation of this disease is angina, or the onset of chest pain with exercise. Macrovascular therapy, in the form of percutaneous coronary intervention (angioplasty) or coronary artery bypass grafting, is available to treat angina; however, patients with downstream blood flow restrictions are not addressed by these interventions. Patients who are poor candidates for a revascularization procedure may be candidates for a biological drug designed to up-regulate the expression of VEGF-A. There are approximately 1.1 million revascularization procedures in the United States each year, and we believe that a significant fraction of these patients could potentially benefit from a less invasive, therapeutic angiogenesis product. Our IHD program is funded and managed by our partner, Edwards Lifesciences, and utilizes the same VEGF-targeted ZFP TF as the PAD program.

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X-linked Severe Combined Immunodeficiency (X-linked SCID)

        X-linked severe combined immunodeficiency is a rare, inherited genetic disease leading to severe T-cell and B-cell dysfunction, severe infection, and death by the age of 2 years. Approximately 50% of these patients harbor a defined mutation in the gene encoding the gamma chain of the interleukin-2 receptor (IL2Rg). Sangamo scientists are using ZFN-mediated gene correction in an effort to repair this genetic lesion in hematopoietic stem cells.

Neuropathic Pain

        Neuropathic pain comprises a set of chronic pain disorders that cannot be connected to previous or underlying trauma as is the case with acute pain. There are several million patients with neuropathic pain in the United States, and the few drugs available show marginal efficacy and many have very significant side effects. Chronic pain is a major and underserved market opportunity and is now an area of intense focus by pharmaceutical researchers owing to the discovery of several new pain-related pathways and drug targets. Recent studies have shown that in chronic pain, certain proteins in nerve cell membranes are up-regulated or over-expressed. Our scientists have identified ZFP TF product candidates that repress the expression of three of these pain targets in cell-based models. We are incorporating these ZFP TFs into gene transfer vectors for testing in pain models during 2004.

Sickle Cell Anemia

        Sickle cell anemia is caused by a mutation in the human ß-globin gene that alters the solubility of hemoglobin under certain physiological conditions. The ensuing disease is characterized by chronic hemolytic anemia with episodes of severe pain and tissue damage often resulting in kidney failure, liver disease, stroke, and other complications. According to the National Heart, Lung and Blood Institute of the NIH, approximately 72,000 people in the U.S. have sickle cell disease. Moreover, approximately 2.5 million Americans carry the sickle cell trait. Although there is still no adequate long-term treatment or cure, some patients may benefit from bone marrow transplantation. However, very few patients have matched donors, and the risks of infection and toxicity are quite high. Sangamo scientists and collaborators are developing methods for ZFN-mediated correction of the ß-globin gene mutation that causes sickle cell anemia. We are collaborating on this program with the Childrens Hospital Research Institute of Oakland.

Cancer

        The American Cancer Society estimates that the incidence of new cancer cases will be approximately 1.3 million in 2004, with 565,500 cancer deaths, accounting for 1 of every 4 deaths in the United States overall. An increasing number of genes are being identified that appear to be important to the development and spread of many forms of cancer. We believe our ZFP TF technology has potential applications in cancer therapy, both in regulating endogenous genes and in activating the body's natural mechanisms for fighting disease. In December 2003, we exclusively licensed the oncolytic adenovirus technology of Onyx Pharmaceuticals for therapeutic applications of ZFP TFs (Armed Therapeutic Viruses™ or ATV™) in cancer. Sangamo scientists are engineering the ATV™ to deliver a ZFP TF that up-regulates granulocyte macrophage colony-stimulating factor (GM-CSF). GM-CSF is a powerful immunostimulator and has been shown to augment anti-tumor immune responses. We believe that the Armed Therapeutic Virus generated by combining these two technologies may have advantages over other cancer immunotherapies in development and may be used to treat cancer both at the tumor site and systemically.

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Amytotrophic Lateral Sclerosis (ALS)

        Amyotrophic lateral sclerosis (ALS), also called Lou Gehrig's disease, is a progressive, fatal neurological disease affecting as many as 20,000 Americans, with 5,000 new cases occurring in the United States each year. The disease belongs to a class of disorders known as motor neuron diseases. ALS occurs when specific nerve cells in the brain and spinal cord that control voluntary movement gradually degenerate. The loss of these motor neurons causes the muscles under their control to weaken and waste away, leading to paralysis. Evidence from preclinical and clinical studies using recombinant insulin-like growth factor I (IGF-I) suggests that the targeted up-regulation of IGF-I could be a viable approach to the treatment of ALS. This program is in the cell-based testing stage for selection of a lead ZFP TF molecule.

Product Development Resources and Infrastructure

        As Sangamo makes its transition to a development-stage biotechnology company, we are building our capabilities in regulatory affairs, quality assurance, manufacturing, and clinical research. Our current plan is to establish these capabilities internally, while relying on third-party contract research organizations and contract manufacturers of ZFP Therapeutic products for toxicology and Phase I/II studies. This will serve to minimize our investment in fixed capital while maximizing our flexibility in our selection of gene transfer systems for the delivery of ZFP TF genes. Our manufacturing and quality assurance personnel will oversee and audit the manufacturing and testing of our experimental products at third-party facilities.

CORPORATE RELATIONSHIPS

        We are applying our ZFP technology platform to several commercial applications in which the products provide ourselves and our strategic partners and collaborators with technical, competitive, and economic advantages. Where and when appropriate, we have established and will continue to pursue ZFP Therapeutic strategic partnerships and Enabling Technology collaborations with selected pharmaceutical and biotechnology companies to fund internal research and development activities and to assist in product development and commercialization.

        We believe the advancement of our first ZFP Therapeutic into a clinical trial in 2004 comes at a timely point in the evolution of the worldwide pharmaceutical industry. Large pharmaceutical companies face revenue growth challenges that may compel them to in-license or acquire emerging therapeutic technologies. Our success in advancing the VEGF program into Phase I/II clinical trials may bring attention to the potential of ZFP Therapeutics to address the non-druggable, yet high-value targets residing within pharmaceutical research laboratories today.

Strategic Partnership with Edwards Lifesciences Corporation

        In January 2000, we announced a therapeutic product development collaboration with Edwards Lifesciences Corporation. Under the agreement, we have licensed to Edwards, on a worldwide, exclusive basis, ZFP Therapeutics for use in the activation of VEGFs and VEGF receptors in ischemic cardiovascular and vascular diseases. Edwards purchased a $5.0 million note that converted, together with accrued interest, into common stock at the time of our initial public offering at the IPO price. In March 2000, Edwards purchased a $7.5 million convertible note in exchange for a right of first refusal for three years to negotiate a license for additional ZFP Therapeutics in cardiovascular and peripheral vascular diseases. That right of first refusal terminated in March 2003. Together with accrued interest, this note converted into common stock at the time of our initial public offering at the IPO price. Through 2001, we received $2 million in research funding from Edwards and a $1.4 million milestone payment for delivery of a lead ZFP Therapeutic product candidate. In November 2002, Edwards signed an amendment to the original agreement and agreed to provide up to $3.5 million in research and

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development funding, including $2.95 million for research and development activities performed in 2002 and 2003. The filing of the IND for PAD in 2004, and the achievement of other research-related milestones in 2003, triggered a total of $1.0 million in milestone payments from Edwards Lifesciences in the first quarter of 2004. We have retained all rights to use our technology for therapeutic applications of VEGF activation outside of ischemic cardiovascular and vascular diseases, including use in wound healing and neurological disorders. Revenues attributable to milestone achievement and collaborative research and development performed under the Edwards agreement were $1.5 million, $2.0 million and $2.5 million for 2003, 2002 and 2001, respectively. The remainder of funding relates to two milestones, one each in the VEGF and phospholamban programs. In the future, Sangamo may receive option fees, milestone payments, royalties and additional research funding from this agreement. During each of 2003, 2002 and 2001, the revenues attributable to milestone achievement and collaborative research and development performed under the Edwards agreement comprised over 10% of total revenues earned by Sangamo.

        Under the Sangamo-Edwards agreement, we have been responsible for advancing product candidates into preclinical animal testing. Edwards has responsibility for preclinical development, regulatory affairs, clinical development, and the sales and marketing of ZFP Therapeutic products developed under the agreement. Sangamo may receive milestone payments in connection with the development and commercialization of the first product under this agreement and may also receive royalties on product sales. As part of the November 2002 amendment to our original agreement, Edwards Lifesciences also entered into a joint collaboration with us to evaluate ZFP TFs for the regulation of a second therapeutic gene target, phospholamban (PLN), for the treatment of congestive heart failure. Under the amended agreement, Sangamo has granted Edwards a right of first refusal to Sangamo's ZFP TFs for the regulation of PLN. This right of first refusal terminates on June 30, 2004. On August 14, 2003 Edwards and Sangamo entered into a Third Amendment to the original license agreement. Under this amendment, Sangamo received payment for research and development milestones associated with the VEGF and PLN programs.

        There is no assurance that the companies will achieve the development and commercialization milestones anticipated in these agreements. Edwards has the right to terminate the agreement at any time upon 90 days written notice. In the event of termination, we retain all payments previously received as well as the right to develop and commercialize all related products.

Exclusive License to Oncolytic Vector Technology from Onyx Pharmaceuticals, Inc.

        In April 2001, we announced a strategic collaboration with Onyx Pharmaceuticals, Inc. to jointly research and develop novel cancer therapeutics by using our ZFP TF technology platform and Onyx's oncolytic adenovirus technology. Under the terms of the agreement, the two companies were to conduct studies on an Armed Therapeutic Virus™ (ATV™) modified to express a ZFP TF, equally share preclinical and clinical development costs, and jointly commercialize products resulting from the alliance. As a result of a change in their strategic direction, Onyx terminated its internal research activities relating to the adenovirus technology and decided not to continue co-development of product candidates under the initial Sangamo-Onyx agreement.

        In December 2003, we announced that Sangamo has exclusively licensed rights to Onyx's oncolytic adenovirus vector technology to independently develop ATV products that encode ZFP TFs. In the initial therapeutic application, we will engineer the ATV to express ZFP TFs designed to up-regulate the expression of human granulocyte macrophage colony-stimulating factor (GM-CSF), a powerful activator of the immune system known to augment anti-tumor immune responses. The license agreement provides us with exclusive worldwide rights for all therapeutic uses of ATVs encoding ZFP TFs that regulate the expression of any target gene. Under the terms of the agreement, Sangamo will have full responsibility for research and commercial development of the ZFP TF ATV. Onyx will receive milestone payments as products advance into and through clinical testing and will receive a

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royalty on product sales. The status of our initial program is reviewed above under "Therapeutic Product Development."

Research Collaboration with Avigen, Inc.

        In October 2002, we announced a collaborative research agreement with Avigen, Inc. to evaluate potential therapies for intractable neuropathic pain based on the combination of Sangamo's ZFP TFs and Avigen's adeno-associated viral vector (AAV) gene delivery technology. Under the terms of the agreements, each company will bear its own expenses and will share any data generated during the term of the agreement. The status of this program is reviewed under "Therapeutic Product Development."

Enabling Technologies for Drug Discovery

        We began marketing our Enabling Technologies to the pharmaceutical and biotechnology industry in 1998. Our Enabling Technology Agreements are based upon the delivery of an engineered ZFP TF which is capable of regulating the expression of a gene for which it is specifically designed and targeted. These agreements typically involve non-exclusive rights to use one or more ZFP TFs for internal research purposes and provide no commercial rights to our core ZFP technology.

        As the emphasis of pharmaceutical research and development has shifted away from target validation to the downstream bottlenecks of the drug discovery process, we have refocused our Enabling Technology products and services toward these critical areas. Specifically, we are supplying our partners with ZFP-engineered cells which over-express a drug target of interest for use in high-throughput compound screening. Typically, pharmaceutical company researchers will use a cDNA encoding the drug target of interest to create these cell-based drug screens. However, if the patent covering such a cDNA is held by a third party, the pharmaceutical company might be prevented from using the cDNA for this purpose. The ZFP-engineered cell-based system allows our pharmaceutical partners to screen against drug targets whose gene sequence is covered by competitor intellectual property.

Enabling Technology Agreements for Pharmaceutical Protein Production

        Protein pharmaceuticals manufactured with genetically modified cells accounted for more than $13.3 billion in annual worldwide sales in 2001. Of this total, monoclonal antibodies accounted for approximately $2.6 billion. Industry experts believe that the introduction of new protein pharmaceuticals may lead to a significant shortfall in production capacity over the next several years.

        Sangamo scientists have demonstrated that ZFP-engineered mammalian cells may be used to increase the yield of bulk pharmaceutical protein from systems used for pharmaceutical antibody production. In January 2002, we announced an agreement with Medarex, Inc. to develop these cell lines to enhance the production yields of monoclonal antibodies. Under this agreement, Medarex provided Sangamo with research funding in 2002 and 2003, and Sangamo will be entitled to milestone payments and, potentially, royalties on sales of Medarex antibodies manufactured with our ZFP TF technology. Medarex will receive a non-exclusive license to the resulting technology, and Sangamo will have the ability to utilize the technology in collaborations with other partners. Revenues attributable to collaborative research and development performed under the Medarex agreements were $600,000 for both 2003 and 2002 and none for 2001. During both 2003 and 2002, the revenues attributable to collaborative research and development performed under the Medarex agreements comprised over 10% of total revenues earned by Sangamo.

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Plant Agriculture

        Sangamo scientists and collaborators have also shown that ZFP TFs can be used to regulate the expression of endogenous genes in plants with similar efficacy as has been repeatedly shown in various mammalian cells and animals. The ability to identify and subsequently regulate gene expression with engineered ZFP TFs may lead to the creation of new plants that increase crop yields; lower production costs; are more resistant to herbicides, pesticides, and plant pathogens; and permit the development of branded agricultural products with unique nutritional and processing characteristics. To commercialize ZFP TFs in agricultural biotechnology, we intend to seek strategic relationships with corporate partners having capabilities in the research, development, and commercialization of agricultural products.

        In January 2001, we announced our first plant agriculture collaboration with Renessen LLC, a joint venture between Cargill and Monsanto Company. Under the terms of the agreement, Sangamo received research funding and milestone payments in 2001 and 2002. Sangamo and Renessen scientists reported on the optimization of a-tocopherol levels in the seed oil of Arabidopsis by using ZFP TFs in the first quarter of 2004.

INTELLECTUAL PROPERTY AND TECHNOLOGY LICENSES

        Our success and ability to compete is dependent in part on the protection of our proprietary technology and information. We rely on a combination of patent, copyright, trademark, and trade secret laws, as well as confidentiality agreements and licensing agreements, to establish and protect our proprietary rights.

        We have licensed intellectual property directed to the design, selection, and use of ZFPs and ZFP TFs for gene regulation from the Massachusetts Institute of Technology, Johnson and Johnson, The Scripps Research Institute, Johns Hopkins University, California Institute of Technology, and Harvard University. These licenses grant us rights to make, use, and sell ZFPs and ZFP TFs under nine families of patent filings. All of these patent families have been filed in the United States, and four have been filed internationally in selected countries. As of January 1, 2004, these patent filings have resulted in 13 issued U.S. patents and 7 granted foreign patents. We believe these licensed patents and patent applications include several of the early and important patent filings directed to design, selection, composition, and use of ZFPs, ZFP TFs, and ZFNs.

        As of December 31, 2003, we had 49 families of internally generated patent filings, including nine U.S. and 13 foreign issued patents, based on internal research conducted by Sangamo and Gendaq Ltd., which we acquired in July 2001. These patent filings are directed to improvements in the design, composition, and use of ZFPs, ZFP TFs, and ZFNs. In the aggregate, we believe that our licensed patents and patent applications, as well as the issued Sangamo patents and pending Sangamo patent applications, will provide us with a substantial proprietary position in our commercial development of ZFP technology. If we are successful in the development and commercialization of our products, we will be obligated by our license agreements to make milestone and royalty payments to some or all of the licensors mentioned above. We believe that total payments under these agreements over the next three years will not exceed $2.0 million. For risks associated with our intellectual property, see "Risk Factors—Because it is difficult and costly to protect our proprietary rights, and third parties have filed patent applications that are similar to ours, we cannot ensure the proprietary protection of our technologies and products." We plan to continue to license and to internally generate intellectual property covering the design, selection, composition, and use of ZFPs; the genes encoding these proteins; and the application of ZFPs, ZFP TFs, and ZFNs in ZFP Therapeutics, Enabling Technology applications, and in plant agriculture research.

        Although we have filed for patents on some aspects of our technology, we cannot assure you that patents will issue as a result of these pending applications or that any patent that has been or may be issued will be upheld. Despite our efforts to protect our proprietary rights, existing patent, copyright,

14

trademark, and trade secret laws afford only limited protection, and we cannot assure you that our intellectual property rights, if challenged, will be upheld as valid or will be adequate to protect our proprietary technology and information. In addition, the laws of some foreign countries may not protect our proprietary rights to the same extent as do the laws of the United States. Attempts may be made to copy or reverse engineer aspects of our technology or to obtain and use information that we regard as proprietary. Our patent filings may be subject to interferences. Litigation or opposition proceedings may be necessary in the future to enforce or uphold our intellectual property rights, to determine the scope of our licenses, or to determine the validity and scope of the proprietary rights of others. The defense and prosecution of intellectual property lawsuits, United States Patent and Trademark Office interference proceedings, and related legal and administrative proceedings in the United States and internationally involve complex legal and factual questions. As a result, these proceedings would be costly and time consuming to pursue and could result in diversion of financial and management resources without any assurance of success.

        We have no outstanding legal actions relating to intellectual property or technology licenses. However, in the future, third parties may assert patent, copyright, trademark, and other intellectual property rights to technologies that are important to our business. Any claims asserting that our products infringe or may infringe proprietary rights of third parties, if determined adversely to us, could significantly harm our business. Any claims, with or without merit, could result in costly litigation, divert the efforts of our technical and management personnel, or require us to enter into or modify existing royalty or licensing agreements, any of which could significantly harm our business. Royalty or licensing agreements, if required, may not be available on terms acceptable to us, if at all. See "Risk Factors—Because it is difficult and costly to protect our proprietary rights, and third parties have filed patent applications that are similar to ours, we cannot ensure the proprietary protection of our technologies and products."

        We have been advised that our technology also gives us and our collaborators independence from third-party gene sequence intellectual property. In general, under United States patent law, a patent may be obtained for any new and useful process, machine, manufacture, or composition of matter. An underlying theme of United States patent law, as related to biotechnology, is that the sequence of a gene, as it exists in the chromosome, is not new, even when newly discovered, unless it is isolated from its normal chromosomal context. As a result, for over a decade, patent courts have held that, to be patentable, a DNA sequence must be purified or isolated. Accordingly, U.S. patent claims can cover only isolated or purified nucleic acid sequences (e.g., a purified DNA fragment or a DNA sequence inserted into a vector). We have been advised that U.S. patent claims do not, and cannot, cover gene sequences as they exist in the chromosome, and international patent law is consistent with U.S. patent law in this regard. Most current methods for over-expression of a gene or protein involve introduction, into a cell, of a vector containing a DNA encoding the protein to be over-expressed. Since such a vector contains isolated sequences which encode the protein, it would be covered by any patent claims to those sequences. In contrast, Sangamo's methods for over-expression utilize ZFP TFs that target endogenous genes as they exist in the chromosome. As a result, our methods do not require the use of isolated DNA sequences encoding the protein to be over-expressed and, our counsel has advised us, do not infringe patent claims to such sequences. Notwithstanding this advice, we realize that others could take a contrary position which could result in litigation. While we believe that we would prevail in any such litigation, the uncertainties involved in litigation generally make it impossible to provide assurance as to the ultimate outcome of such matters. See "Risk Factors—Because it is difficult and costly to protect our proprietary rights, and third parties have filed patent applications that are similar to ours, we cannot ensure the proprietary protection of our technologies and products."

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COMPETITION

        Sangamo is the worldwide leader in the research, development, and commercialization of DNA binding proteins for the regulation of gene expression and gene correction. We are aware of many companies focused on other methods for regulating gene expression and a limited number of commercial and academic groups pursuing the development of ZFP gene regulation and gene correction technology. The field of applied gene regulation is highly competitive, and we expect competition to persist and intensify in the future from a number of different sources, including pharmaceutical, agricultural, and biotechnology companies; academic and research institutions; and government agencies that will seek to develop ZFPs as well as technologies that will compete with our ZFP technology platform.

        In July 2001, we strengthened our competitive position by completing our acquisition of Gendaq Ltd. Gendaq scientists had also focused their research efforts on regulating genes through the engineering of ZFPs, and they brought significant additional know-how and intellectual property into Sangamo. Despite the Gendaq acquisition and our strong presence in the field of ZFP technology and intellectual property, any products that we develop with our ZFP TF technology will participate in highly competitive markets. Many of our potential competitors in these markets, either alone or with their collaborative partners, may have substantially greater financial, technical, and personnel resources than we do, and they may succeed in developing technologies and products that would render our technology obsolete or non-competitive. In addition, many of those competitors may have significantly greater experience than we do in their respective fields.

        Accordingly, our competitors may succeed in obtaining patent protection, receiving FDA approval, or commercializing ZFP Therapeutics or other competitive products before us. If we commence commercial product sales, we may be competing against companies with greater marketing and manufacturing capabilities, areas in which we have limited or no experience. In addition, any product candidate that we successfully develop may compete with existing products that have long histories of safe and effective use.

        Competition may also arise from other drug development technologies and methods of preventing or reducing the incidence of disease, small-molecule therapeutics, or other classes of therapeutic agents, including monoclonal antibodies, purified proteins, gene therapy, and other nucleic acid technologies such as antisense RNA and siRNA. Furthermore, there are alternative approaches to gene correction that could prove technically superior to our gene correction technology or be commercialized more rapidly.

        We expect to face intense competition from other companies for collaborative arrangements with pharmaceutical, biotechnology, and agricultural companies; for establishing relationships with academic and research institutions; and for licenses to proprietary technology. These competitors, either alone or with their collaborative partners, may succeed in developing technologies or products that are more effective or less costly than ours.

        Our ability to compete successfully will depend, in part, on our ability to:

•

develop proprietary products;



•

obtain access to gene transfer technology on commercially reasonable terms;



•

develop and maintain products that reach the market first and are technologically superior to or are of lower cost than other products in the market;



•

attract and retain scientific and product development personnel;



•

obtain and enforce patents, licenses, or other proprietary protection for our products and technologies;

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•

obtain required regulatory approvals; and



•

formulate, manufacture, market, and sell any product that we develop.

GOVERNMENT REGULATION

        Our partner, Edwards Lifesciences, submitted a Phase I/II clinical protocol for review by the Recombinant DNA Advisory Committee (RAC) of the NIH in the fourth quarter of 2003 and filed the first ZFP Therapeutic IND application with the FDA in February 2004. We have not applied for regulatory approvals with respect to any of our other technologies or products under development. We anticipate that the research, development, and commercialization of any therapeutic products developed, either alone or with our strategic partners or collaborators, will be subject to extensive regulation in the United States and other countries.

        Before marketing in the United States, any therapeutic or pharmaceutical products developed by us must undergo rigorous preclinical testing and clinical trials and an extensive regulatory clearance process implemented by the FDA under the federal Food, Drug and Cosmetic Act. The FDA regulates, among other things, the development, testing, manufacture, safety, efficacy, record keeping, labeling, storage, approval, advertising, promotion, sale, and distribution of biopharmaceutical products. The regulatory review and approval process, which includes preclinical testing and clinical trials of each product candidate, is lengthy, expensive, and uncertain. Securing FDA approval requires the submission of extensive preclinical and clinical data and supporting information to the FDA for each indication to establish a product candidate's safety and efficacy. The approval process takes many years, requires the expenditure of substantial resources, involves post-marketing surveillance, and may involve ongoing requirements for post-marketing studies. Before commencing clinical investigations in humans, we must submit to, and receive approval from, the FDA of an Investigational New Drug application.

        Outside the United States, our ability to market a product is contingent upon receiving a marketing authorization from the appropriate regulatory authorities. The requirements governing the conduct of clinical trials, marketing authorization, pricing, and reimbursement vary widely from country to country. At present, foreign marketing authorizations are applied for at a national level; although, within the European Union (EU), registration procedures are available to companies wishing to market a product in more than one EU member state. If the regulatory authority is presented with adequate evidence of safety, quality, and efficacy, they will grant a marketing authorization. This foreign regulatory approval process involves all of the risks associated with FDA clearance discussed above.

        We have begun to hire personnel with expertise in regulatory affairs to assist us in obtaining appropriate regulatory approvals as required. In 2003, we hired employees with experience in preclinical and clinical development of therapeutic programs and products. We also intend to work with our strategic partners and collaborators that have experience in regulatory affairs to assist us in obtaining regulatory approvals for collaborative products. See Risk Factors—"Our potential therapeutic products are subject to a lengthy and uncertain regulatory process, and if these potential products are not approved, we will not be able to commercialize those products" and "Regulatory approval, if granted, may be limited to specific uses or geographic areas which could limit our ability to generate revenues."

RESEARCH AND DEVELOPMENT EXPENDITURES

        Over the past three fiscal years, research and development expenditures have consisted primarily of salaries and related personnel expenses, laboratory supplies, allocated facilities costs, subcontracted research expenses, and expenses for patent prosecution, trademark registration and technology licenses. Research and development costs incurred in connection with company collaborator funded activities are expensed as incurred. We believe that continued investment in research and development is critical to attaining our strategic objectives. We expect these expenses will increase significantly as we focus

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increasingly on development of ZFP Therapeutics. The Company is also developing zinc finger nucleases (ZFN) for therapeutic gene correction as a treatment and possible cure for certain monogenic diseases. Additionally, in order to develop ZFP TFs as commercially relevant therapeutics, we expect to expend additional resources for expertise in the manufacturing, regulatory affairs and clinical research aspects of biotherapeutic development.

EMPLOYEES

        As of February 18, 2004, we had 57 full-time employees, all of which are located in Richmond, California. None of our employees is represented by a collective bargaining agreement, nor have we experienced work stoppages. We believe that our relations with our employees are good.

AVAILABLE INFORMATION

        Sangamo can be found on the internet at http://www.sangamo.com and http://www.expressinglife.com. We make available free of charge, on or through our internet site, our annual, quarterly, and current reports and any amendments to those reports filed or furnished pursuant to Section 13(a) of the Exchange Act as soon as reasonably practicable after we electronically file such material with, or furnish it to, the SEC. Information contained in Sangamo's internet site is not part of this report.

RISKS RELATED TO OUR BUSINESS

        We are increasing the focus of our research and development programs on human therapeutics, which may increase operating expenditures and the uncertainty of our business. We are increasing the emphasis and focus of our research and development activities on ZFP Therapeutics and are moving away from our historic emphasis on Enabling Technology agreements. In the short term, this change in resource allocation will reduce our revenues and increase operating expenditures due to larger financial outlays to fund preclinical studies, manufacturing, and clinical research. The transition will also increase the visibility of our lead therapeutic programs and the potential impact on the stock price of news releases relating to these programs.

        Our partner, Edwards Lifesciences, is planning to initiate Phase I/II clinical testing in our lead ZFP Therapeutic program, and ZFP Therapeutics have never before been tested in humans. If our lead ZFP Therapeutic fails its initial safety study, it could damage our ability to attract new investors and corporate partners. The Phase I/II study of our lead therapeutic will be a highly visible test of the Company's ZFP Therapeutic approach. Since we have increased our focus on ZFP Therapeutic research and development, investors will increasingly assess the value of the Company's technology based on the continued progress of ZFP Therapeutic products into and through clinical trials. If the initial safety study of our lead therapeutic was halted due to safety concerns, this would negatively affect the value of the Company's stock.

        We are conducting proprietary research to discover ZFP Therapeutic product candidates. These programs increase our risk of product failure, may significantly increase our research expenditures, and may involve conflicts with our collaborators and strategic partners. Conducting proprietary research programs may not generate corresponding revenue and may create conflicts with our collaborators or strategic partners. The implementation of this strategy will involve substantially greater business risks and the expenditure of significantly greater funds than our historic research activities. In addition, these programs will require substantial commitments of time from our management and staff. Moreover, we have no experience in commercial-scale manufacturing and marketing of therapeutic products, and we currently do not have the infrastructure or capability to manufacture therapeutic products on a commercial scale. In order for us to commercialize these products directly, we would need to develop, or obtain through outsourcing arrangements, the capability to execute all of these

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functions. We do not have these capabilities, and we may not be able to develop or otherwise obtain the requisite preclinical, clinical, regulatory, manufacturing, marketing, and sales capabilities.

        In addition, disagreements with our collaborators or strategic partners could develop over rights to our intellectual property with respect to our proprietary research activities. Any conflict with our collaborators or strategic partners could reduce our ability to enter into future collaboration or strategic partnering agreements and negatively impact our relationship with existing collaborators and strategic partners, which could reduce our revenue and delay or terminate our product development.

        Our potential therapeutic products are subject to a lengthy and uncertain regulatory process, and if these potential products are not approved, we will not be able to commercialize those products. The FDA must approve any human therapeutic products before they can be marketed in the United States. The process for receiving regulatory approval is long and uncertain, and a potential product may not withstand the rigors of testing under the regulatory approval processes.

        Before commencing clinical trials in humans, we or our commercial partner must submit an Investigational New Drug (IND) application to the FDA. The FDA has 30 days to comment on the IND. If the FDA does not comment on the IND, we or our commercial partner may begin clinical trials.

        Clinical trials are subject to oversight by institutional review boards and the FDA and:

•

must be conducted in conformance with the FDA's good clinical practices and other applicable regulations;



•

must meet requirements for institutional review board oversight;



•

must meet requirements for informed consent;



•

are subject to continuing FDA oversight;



•

may require large numbers of test subjects; and



•

may be suspended by us, our commercial partner, or the FDA at any time if it is believed that the subjects participating in these trials are being exposed to unacceptable health risks or if the FDA finds deficiencies in the IND or the conduct of these trials.

        While we have stated our intention to file IND applications during the next several years, this is only a statement of intent, and we may not be able to do so because the associated product candidates may not meet the necessary preclinical requirements. In addition, there can be no assurance that, once filed, an IND application will result in the actual initiation of clinical trials.

        In addition, our proposed clinical studies will require review from the Recombinant DNA Advisory Committee, or RAC, which is the advisory board to the National Institutes of Health, or NIH, focusing on clinical trials involving gene transfer.

        Our gene regulation technology is relatively new, and if we are unable to use this technology in all our intended applications, it would limit our revenue opportunities. Our technology involves a relatively new approach to gene regulation. Although we have generated ZFP TFs for hundreds of gene sequences, we have not created ZFP TFs for all gene sequences and may not be able do so, which could limit the usefulness of our technology. In addition, while we have demonstrated the function of engineered ZFP TFs in mammalian cell culture, yeast, insects, plants, and animals, we have not yet done so in humans, and the failure to do so could restrict our ability to develop commercially viable products. If we, and our collaborators or strategic partners, are unable to extend our results to new commercially important genes, experimental animal models, and human clinical studies, we may be unable to use our technology in all its intended applications. Also, delivery of ZFP TFs into cells and organisms, including humans, in these and other environments is limited by a number of technical

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challenges, which we may be unable to surmount. This is a particular challenge for therapeutic applications of our technology that will require the use of strictly regulated gene transfer systems that may be unavailable to us or unsuitable for delivery of our ZFP TFs for a particular therapeutic application.

        The expected value and utility of our ZFP TFs is in part based on our belief that the transcriptional regulation of gene expression and targeted gene correction may enable us to develop a new therapeutic approach as well as to help scientists better understand the role of human, animal, and other genes in disease and to aid their efforts in drug discovery and development. We also believe that the regulation of gene expression and targeted gene insertion will have utility in agricultural applications. There is only a limited understanding of the role of specific genes in all these fields. Life sciences companies have developed or commercialized only a few products in any of these fields based on results from genomic research or the ability to regulate gene expression. We, our collaborators, or our strategic partners may not be able to use our technology to identify and validate drug targets or to develop commercial products in the intended markets.

        We are currently engaged in the research and development of a new application of our technology platform: ZFP-mediated gene correction. Using this technique, Sangamo scientists have engineered gene-specific ZFPs to cut DNA at a specific site within a target gene, and to then replace the adjacent sequences with new DNA. In so doing, we are attempting to "repair" or "correct" an abnormal or disease-related mutation or DNA sequence. ZFP-mediated gene correction is at an early stage of development. Our scientists have shown ZFP-mediated gene correction to work in isolated cells; however, a significant amount of additional research will be needed before this technique can be evaluated in animals or plants and subsequently tested for applications in human healthcare and plant agriculture.

        Even if our technology proves to be effective, it still may not lead to commercially viable products. Even if our collaborators or strategic partners are successful in using our ZFP technology in drug discovery, protein production, therapeutic development, or plant agriculture, they may not be able to commercialize the resulting products or may decide to use other methods competitive with our technology. To date, no company has received marketing approval or has developed or commercialized any therapeutic or agricultural products based on our technology. The failure of our technology to provide safe, effective, useful, or commercially viable approaches to the discovery and development of these products would significantly limit our business and future growth and would adversely affect our value.

        We may be unable to license gene transfer technologies that we may need to commercialize our ZFP TF technology. In order to regulate an endogenous gene, the ZFP TF must be efficiently delivered to a cell. We have licensed certain gene transfer technologies for use with our Enabling Technologies in pharmaceutical discovery applications. We are evaluating these systems and other technologies which may need to be used in the delivery of ZFP TFs into cells for in vitro and in vivo applications, including ZFP Therapeutics. However, we may not be able to license the gene transfer technologies required to develop and commercialize our ZFP Therapeutics. We have not developed our own gene transfer technologies, and we rely on our ability to enter into license agreements to provide us with rights to the necessary gene transfer technology. The inability to obtain a license to use gene transfer technologies with entities which own such technology on reasonable commercial terms, if at all, could delay or prevent the preclinical evaluation, clinical testing, and/or commercialization of our therapeutic product candidates.

        Adverse events in the field of gene therapy may negatively impact regulatory approval or public perception of our potential products. Our potential therapeutic products are delivered to patients as gene-based drugs, or gene therapy. The clinical and commercial success of our potential products will depend in part on public acceptance of the use of gene therapy for the prevention or treatment of

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human diseases. Public attitudes may be influenced by claims that gene therapy is unsafe, and, consequently, our products may not gain the acceptance of the public or the medical community. Negative public reaction to gene therapy in general could result in greater government regulation and stricter labeling requirements of gene therapy products, including any of our products, and could cause a decrease in the demand for any products we may develop.

        Our stock price is also influenced by public perception. Recent reports of serious adverse events in a retroviral gene transfer trial for infants with severe combined immunodeficiency (SCID) in France and subsequent FDA actions putting related trials on hold in the United States had a significant negative impact on the public perception and stock price of certain companies involved in gene therapy. Stock prices of these companies declined whether or not the specific company was involved with retroviral gene transfer for the treatment of infants with SCID, or whether the specific company's clinical trials were put on hold in connection with these events.

        Other potential adverse events in the field of gene therapy may occur in the future that could result in greater governmental regulation of our potential products and potential regulatory delays relating to the testing or approval of our potential products.

        We are at the development phase of operations and may not succeed or become profitable. We began operations in 1995 and are in the early phases of ZFP Therapeutic product development. We have incurred significant losses to date, and our revenues have been generated from Enabling Technology agreements, strategic partners, and federal government research grants. In 2003, we have placed more emphasis on therapeutic activities and related strategic partnerships and less emphasis on our Universal GeneTools® collaborations. Our business is subject to all of the risks inherent in the development of a new technology, which include the need to:

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attract and retain qualified scientific and technical staff and management, particularly scientific staff with expertise to develop our early-stage technology into therapeutic products;



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obtain sufficient capital to support the expense of developing our technology platform and developing, testing, and commercializing products;



•

develop a market for our products;



•

successfully transition from a company with a research focus to a company capable of supporting commercial activities; and



•

attract and enter into research collaborations with research and academic institutions and scientists.

        Commercialization of our technologies will depend, in large part, on strategic partnering with other companies. If we are not able to find strategic partners in the future or our strategic partners do not diligently pursue product development efforts, we may not be able to develop our technologies or products, which could slow our growth and decrease our value. We expect to rely, to a significant extent, on our strategic partners to provide funding in support of our research and to perform independent research and preclinical and clinical testing. Our technology is broad based, and we do not currently possess the resources necessary to fully develop and commercialize potential products that may result from our technologies or the resources or capabilities to complete the lengthy marketing approval processes that may be required for the products. Therefore, we plan to rely on strategic partnerships to help us develop and commercialize ZFP Therapeutic products. If those partners are unable or unwilling to advance our programs, or if they do not diligently pursue product approval, this may slow our progress and defer our revenues. Our partners may sublicense or abandon development programs, which would cause associated product development to slow or cease. There can be no assurance that we will be able to establish additional strategic collaborations for ZFP Therapeutic product development. We may require significant time to secure additional collaborations or strategic

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partners because we need to effectively market the benefits of our technology to these future collaborators and strategic partners, which use the time and efforts of research and development personnel and our management. Further, each collaboration or strategic partnering arrangement will involve the negotiation of terms that may be unique to each collaborator or strategic partner. These business development efforts may not result in a collaboration or strategic partnership.

        If we do not enter into additional strategic partnering agreements, we will experience reduced revenues and may not develop or commercialize our products. The loss of our current or any future strategic partnering agreements would not only delay or terminate the potential development or commercialization of products we may derive from our technologies, but it may also delay or terminate our ability to test ZFP TFs for specific genes. If any strategic partner fails to conduct the collaborative activities successfully and in a timely manner, the preclinical or clinical development or commercialization of the affected product candidates or research programs could be delayed or terminated.

        Our existing strategic partnering agreements are, and we would expect any future arrangement to be, based on the achievement of milestones. Under the strategic partnering agreements, we expect to receive revenue for the research and development of a ZFP Therapeutic product based on achievement of specific milestones. Achieving these milestones will depend, in part, on the efforts of our strategic partner as well as our own. In contrast, our historic Enabling Technology agreements only pay us to supply ZFP TFs for the collaborator's independent use, rather than for future results of the collaborator's efforts. If we, or any strategic partner, fail to meet specific milestones, then the strategic partnership may be terminated, which could decrease our revenues.

        If our competitors develop, acquire, or market technologies or products that are more effective than ours, this would reduce or eliminate our commercial opportunity. Any products that we or our collaborators or strategic partners develop by using our ZFP TF technology platform will enter into highly competitive markets. Even if we are able to generate ZFP Therapeutics that are safe and effective for their intended use, competing technologies may prove to be more effective or less expensive, which, to the extent these competing technologies achieve market acceptance, will limit our revenue opportunities. In some cases, competing technologies have proven to be satisfactorily effective and less expensive, as has been the case with technologies competitive with our Universal Gene Tools®. The effectiveness of these competing products has reduced the revenues generated by our Universal Gene Tools®. Competing technologies may include other methods of regulating gene expression. ZFP TFs have broad application in the life sciences and compete with a broad array of new technologies and approaches being applied to genetic research by many companies. Competitive technologies include those used to analyze the expression of genes in cells or tissues, determine gene function, discover new genes, analyze genetic information, and regulate genes. Competing proprietary technologies with our product development focus include:

•

For ZFP Therapeutics: small molecule drugs, monoclonal antibodies, recombinant proteins, antisense and siRNA approaches



•

For our Enabling Technology Applications:



•

Universal GeneTools®: antisense, siRNA



•

high throughput screening: cDNA, naturally occurring cell lines



•

protein production: gene amplification



•

In addition to possessing competing technologies, our competitors include biotechnology companies with:



•

substantially greater capital resources than ours;

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•

larger research and development staffs and facilities than ours;



•

greater experience in product development and in obtaining regulatory approvals and patent protection; and



•

These organizations also compete with us to:



•

attract qualified personnel;



•

attract parties for acquisitions, joint ventures or other collaborations; and



•

license the proprietary technologies of academic and research institutions that are competitive with our technology, which may preclude us from pursuing similar opportunities.

Accordingly, our competitors may succeed in obtaining patent protection or commercializing products before us. In addition, any products that we develop may compete with existing products or services that are well established in the marketplace.

        Our collaborators or strategic partners may decide to adopt alternative technologies or may be unable to develop commercially viable products with our technology, which would negatively impact our revenues and our strategy to develop these products. Our collaborators or strategic partners may adopt alternative technologies, which could decrease the marketability of ZFP technology. Additionally, because many of our collaborators or strategic partners are likely to be working on more than one development project, they could choose to shift their resources to projects other than those they are working on with us. If they do so, that would delay our ability to test our technology and would delay or terminate the development of potential products based on our ZFP technology. Further, our collaborators and strategic partners may elect not to develop products arising out of our collaborative and strategic partnering arrangements or to devote sufficient resources to the development, manufacturing, marketing, or sale of these products. If any of these events occur, we may not be able to develop our technologies or commercialize our products.

        Early commercial application in drug discovery research of our engineered ZFP TFs delivered to our Universal GeneTools® collaborators have not produced useful results in every case. In the past, some of our Universal GeneTools® collaborators were unable to substantiate the effects of our gene regulation technology. Generally, failures were re-evaluated at Sangamo by using our most current approach. In some cases, additional ZFP TFs were designed and tested for these targets, and data were generated at Sangamo, or by our partners, confirming the ability to regulate these targets. However, there can be no assurance that we will be able to regulate all gene targets. Although we have been able to achieve targeted activation or repression of numerous genes, the degree of activation or repression is not always sufficient to allow our collaborators to realize their objectives. If we are unsuccessful in engineering ZFP TFs that achieve positive results for our collaborators or strategic partners, this would significantly harm our business by reducing our revenues.

        We anticipate continuing to incur operating losses for the next several years. If material losses continue for a significant period, we may be unable to continue our operations. We have generated operating losses since we began operations in 1995. The extent of our future losses and the timing of profitability are uncertain, and we expect to incur losses for the foreseeable future. We have been engaged in developing our ZFP TF technology since inception, which has and will continue to require significant research and development expenditures. To date, we have generated our revenues from Universal GeneTools® collaboration agreements, strategic partnering agreements, and federal government research grants. As of December 31, 2003, we had an accumulated deficit of approximately $83.3 million. We expect to incur losses for the foreseeable future. These losses will increase as we expand and extend our research and development activities into human therapeutic product

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development. If the time required to generate significant product revenues and achieve profitability is longer than we currently anticipate, we may not be able to sustain our operations.

        We may be unable to raise additional capital should it become necessary, which would harm our ability to develop our technology and products. We have incurred significant operating losses and negative operating cash flows since inception and have not achieved profitability. We expect capital outlays and operating expenditures to increase over the next several years as we expand our infrastructure and research and ZFP Therapeutic product development activities. While we believe our financial resources will be adequate to sustain our current operations at least through 2005, we may seek additional sources of capital through equity or debt financing. In addition, as we focus our efforts on proprietary human therapeutics, we will need to seek FDA approval of potential products, a process that could cost in excess of $100 million per product. We cannot be certain that we will be able to obtain financing on terms acceptable to us, or at all. If adequate funds are not available, our business and our ability to develop our technology and ZFP Therapeutic products would be harmed.

        Our stock price has been volatile and may continue to be volatile, which could result in substantial losses for investors. Volatility in our common stock could cause stockholders to incur substantial losses. An active public market for our common stock may not be sustained, and the market price of our common stock may continue to be highly volatile. The market price of our common stock has fluctuated significantly in response to the following factors, some of which are beyond our control:

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changes in market valuations of similar companies;



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deviations in our results of operations from the guidance given by us or estimates of securities analysts;



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announcements by us or our competitors of new or enhanced products, technologies or services or significant contracts, acquisitions, strategic relationships, joint ventures or capital commitments;



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regulatory developments;



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additions or departures of key personnel;



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announcements by us or our partners providing updates on the progress or development status of ZFP Therapeutics; and



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future sales of our common stock or other securities by the company, management or directors, liquidation of institutional funds that comprised large holdings of Sangamo stock.

        Failure to attract, retain, and motivate skilled personnel and cultivate key academic collaborations will delay our product development programs and our research and development efforts. We are a small company with 57 full-time employees as of February 18, 2004, and our success depends on our continued ability to attract, retain, and motivate highly qualified management and scientific personnel and our ability to develop and maintain important relationships with leading research and academic institutions and scientists. Competition for personnel and academic and other research collaborations is intense. The success of our technology development programs depends on our ability to attract and retain highly trained personnel. If we lose the services of personnel with the necessary skills, it could significantly impede the achievement of our research and development objectives. If we fail to negotiate additional acceptable collaborations with academic and other research institutions and scientists, or if our existing collaborations are unsuccessful, our ZFP Therapeutic development programs may be delayed or may not succeed.

        If conflicts arise between us and our collaborators, strategic partners, scientific advisors, or directors, these parties may act in their self-interest, which may limit our ability to implement our strategies. If conflicts arise between our corporate or academic collaborators, strategic partners, or

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scientific advisors or directors and us, the other party may act in its self-interest, which may limit our ability to implement our strategies. Some of our academic collaborators and strategic partners are conducting multiple product development efforts within each area that is the subject of the collaboration with us. Our collaborators or strategic partners, however, may develop, either alone or with others, products in related fields that are competitive with the products or potential products that are the subject of these collaborations. Competing products, either developed by the collaborators or strategic partners or to which the collaborators or strategic partners have rights, may result in the withdrawal of partner support for our product candidates.

        Some of our collaborators or strategic partners could also become competitors in the future. Our collaborators or strategic partners could develop competing products, preclude us from entering into collaborations with their competitors, fail to obtain timely regulatory approvals, terminate their agreements with us prematurely, or fail to devote sufficient resources to the development and commercialization of products. Any of these developments could harm our product development efforts.

        Because it is difficult and costly to protect our proprietary rights, and third parties have filed patent applications that are similar to ours, we cannot ensure the proprietary protection of our technologies and products. Our commercial success will depend in part on obtaining patent protection of our technology and successfully defending these patents against third-party challenges. The patent positions of pharmaceutical and biotechnology companies can be highly uncertain and can involve complex legal and factual questions. No consistent policy regarding the breadth of claims allowed in biotechnology patents has emerged to date. Accordingly, we cannot predict the breadth of claims allowed in patents we own or license.

        We are a party to various license agreements that give us rights under specified patents and patent applications. Our current licenses, as our future licenses frequently will, contain performance obligations. If we fail to meet those obligations, the licenses could be terminated. If we are unable to continue to license these technologies on commercially reasonable terms, or at all, we may be forced to delay or terminate our product development and research activities.

        With respect to our present and any future sublicenses, since our rights derive from those granted to our sublicensor, we are subject to the risk that our sublicensor may fail to perform its obligations under the master license or fail to inform us of useful improvements in, or additions to, the underlying intellectual property owned by the original licensor.

        We are unable to exercise the same degree of control over intellectual property that we license from third parties as we exercise over our internally developed intellectual property. We generally do not control the prosecution of patent applications that we license from third parties; therefore, the patent applications may not be prosecuted in a timely manner.

        The degree of future protection for our proprietary rights is uncertain, and we cannot ensure that: