Exhibit 99.1

Arena Reports Third Quarter Financial Results with Strong Cash Position, Advancing Etrasimod Into a Phase 3 Registrational Program in Atopic Dermatitis 

- Delivered compelling topline results from ADVISE Ph 2b trial evaluating etrasimod in atopic dermatitis; advancing into a Ph 3 registrational program 

- Initiated etrasimod trials: ELEVATE UC 12 Ph 3, GLADIATOR UC and alopecia areata Ph 2 

- Completed enrollment of CAPTIVATE Ph 2b trial evaluating olorinab in irritable bowel syndrome (IBS) pain, topline data expected Q1 2020 

- Completed first-in-human Ph 1 trial for APD418 

- Completed launch of Longboard Pharmaceuticals (formerly Arena Neuroscience)  

- Cash, cash equivalents and marketable securities of ~$1.2bn as of September 30, 2020 

- Arena to host conference call and webcast today at 4:30 PM ET to discuss ADVISE results and corporate updates  

SAN DIEGO, Calif., November 9, 2020 - Arena Pharmaceuticals, Inc. (Nasdaq: ARNA) today provided a corporate update and reported financial results for the third quarter ended September 30, 2020. 

"Over the quarter we made significant progress across our pipeline – most importantly with the results from the ADVISE trial giving us confidence to move expeditiously into a registrational program. Additionally, we initiated the ELEVATE UC 12, GLADIATOR UC and alopecia areata trials. We completed enrollment of the CAPTIVATE Phase 2b trial for olorinab, keeping us on track for expected topline data in Q1. In addition, we have completed the Phase 1 trial of APD418 and have plans to initiate our Phase 2 program in 2021. We also successfully spun-off our neurology franchise with the inception of Longboard Pharmaceuticals, to help unlock the value of those assets," said Amit D. Munshi, President and CEO of Arena. "We are optimistic about the next 12-18 months as we continue our efforts to build long-term value for all of our stakeholders and execute on key catalysts."  

Program Updates 

Business Update 

Financial Update 

Third Quarter 2020 Financial Results  

Financial Outlook for 2020 

Arena’s 2020 financial guidance range: 

Conference Call & Webcast Information 

Arena will host a conference call and live webcast the investment community today, Monday, November 9, 2020, at 4:30 PM ET, to discuss the financial results and corporate update. 

When: Monday, November 9, 2020, at 4:30 PM ET 

Dial-in: (877) 643-7155 (United States) or (914) 495-8552 (International) 

Conference ID: 6166976 

Please join the conference call at least 20 minutes early to register. You can access the live webcast under the investor relations section of Arena’s website at: www.arenapharm.com. A replay of the event will be archived under the investor relations section of Arena’s website for 30 days shortly after the call. 

About Arena Pharmaceuticals 

ARENA Pharmaceuticals is a team with a singular purpose – deliver our important medicines to patients.  

In a rapidly changing global market, we work with a sense of urgency every day to understand the needs of all our stakeholders, identify bold, sometimes disruptive, ideas to get our medicines to patients, and relentlessly execute until it’s done.  

ARENA - Care More. Act Differently. 

Etrasimod, olorinab and APD418 are investigational compounds that are not approved for any use in any country. 

Forward-Looking Statements 

Certain statements in this press release are forward-looking statements that involve a number of risks and uncertainties. Such forward-looking statements may be identified by words such as “expected,” “will,” “long-term,” “outlook,” and “guidance” and include, without limitation, statements about the following: Arena’s clinical programs, including plans to advance etrasimod into a registrational program in atopic dermatitis, expectations regarding enrollment of study participants and the timing of data readouts for ongoing and anticipated trials, and expectations for the commencement of additional trials; the statements under “Program Updates” above; and Arena’s financial outlook and guidance, including expectations regarding cash to be used in operating activities and the rate of change thereof. For such statements, Arena claims the protection of the Private Securities Litigation Reform Act of 1995. Actual events or results may differ materially from Arena’s expectations. Factors that could cause actual results to differ materially from the forward-looking statements include, but are not limited to, the following: topline data may not accurately reflect the complete results of a particular study or trial; results of clinical trials and other studies are subject to different interpretations and may not be predictive of future results; clinical trials and other studies may not proceed at the time or in the manner expected or at all; the timing and outcome of research, development and regulatory review is uncertain, and Arena’s drug candidates may not advance in development or be approved for marketing; enrolling patients in Arena’s ongoing and intended clinical trials is competitive and challenging; the duration and severity of the coronavirus disease (COVID-19) pandemic, including but not limited to the impact on Arena’s clinical operations, the operations of Arena’s suppliers, partners, collaborators, licensees, and capital markets, which in each case remains uncertain; risks related to developing and commercializing drugs; Arena will need additional funds to advance all of its programs; the impact of competition; risks related to unexpected or unfavorable new data; the risk that regulatory agencies may interpret or weigh the importance of data differently and reach different conclusions than Arena or others, request additional information, have additional recommendations or change their guidance or requirements before or after approval; satisfactory resolution of litigation or other disagreements with others; and risks related to the enforcement of Arena’s and third parties’ intellectual property rights. Additional factors that could cause actual results to differ materially from those stated or implied by Arena’s forward-looking statements are disclosed in Arena’s filings with the Securities and Exchange Commission (SEC), including but not limited to Arena’s Annual Report on Form 10-K for the year ended December 31, 2019, which was filed with the SEC on February 27, 2020, and Arena’s Quarterly Report on Form 10-Q for the quarter ended June 30, 2020, which was filed with the SEC on August 5, 2020. These forward-looking statements represent Arena’s judgment as of the time of this release. Arena disclaims any intent or obligation to update these forward-looking statements, other than as may be required under applicable law. 

Corporate Contacts:  

Patrick Malloy 

Arena Pharmaceuticals, Inc.  

Vice President, Investor Relations & Corporate Communications 

pmalloy@arenapharm.com 

847.987.4878 

Megan E. Knight 
Arena Pharmaceuticals, Inc. 
Director, Investor Relations  
mknight@arenapharm.com 

858.210.3635 

(Tables Follow)

Arena Pharmaceuticals, Inc.

Condensed Consolidated Statements of Operations

(In thousands, except per share amounts)

Arena Pharmaceuticals, Inc.

Condensed Consolidated Balance Sheet Data

(In thousands)

(Unaudited)

¹ The Condensed Consolidated Balance Sheet Data has been derived from the audited financial statements as of that date.