Five Prime to Present Phase 2 FIGHT Trial Results of Bemarituzumab at American Society of Clinical Oncology (ASCO) Gastrointestinal (GI) Cancers Virtual Annual Symposium

Five Prime Therapeutics, Inc. (NASDAQ: FPRX), a clinical-stage biotechnology company focused on developing immune modulators and precision therapies for solid tumor cancers, today announced that detailed results from the global, randomized, double-blind placebo-controlled Phase 2 FIGHT trial evaluating bemarituzumab plus mFOLFOX6 chemotherapy in patients with fibroblast growth factor receptor 2b-positive (FGFR2b+), non HER2 positive (non HER2+) advanced gastric and gastroesophageal junction (GEJ) cancer will be featured during an oral podium presentation on January 15, 2021, at the ASCO Gastrointestinal Cancers Symposium being held virtually from January 15-17, 2021.

On November 10, 2020, Five Prime announced that the FIGHT trial met all three efficacy endpoints with bemarituzumab in combination with mFOLFOX6 chemotherapy providing statistically significant and clinically meaningful improvements in progression-free survival, overall survival, and objective response rate compared with mFOLFOX6 chemotherapy plus placebo in the front-line setting of patients with FGFR2b+, non HER2+ advanced gastric or GEJ cancer.

Bemarituzumab is the first and only investigational treatment targeting FGFR2b+ tumors. FGFR2b is overexpressed in approximately 30 percent of non HER2+ gastric and GEJ cancers. For these patients, no new front-line therapies have been approved in over a decade and systemic chemotherapy remains the standard of care. Five Prime and Roche Tissue Diagnostics (formerly Ventana Medical Systems) have also found that FGFR2b is overexpressed in numerous other cancers, including squamous non-small cell lung cancer, triple negative breast cancer, ovarian cancer, pancreatic cancer and intrahepatic cholangiocarcinoma. This represents additional potential areas for development of bemarituzumab beyond gastric and GEJ cancer.

The Company will host a conference call and live audio webcast on Friday, January 15, 2021 at 4:30pm (EST) / 1:30pm (PST) to review highlights from the presentation and will feature members of the Five Prime management team and Zev A. Wainberg, M.D., Associate Professor of Medicine at UCLA, Co-director of the Gastrointestinal Oncology Program and Director of Early Phase Clinical Research at the Jonsson Comprehensive Cancer Center, and a principal investigator of the trial.

Oral Presentation Details:

• Title: Randomized Double-blind Placebo-Controlled Phase 2 Study of Bemarituzumab Combined with Modified FOLFOX6 (mFOLFOX6) in 1st Line (1L) Treatment of Advanced Gastric/Gastroesophageal Junction Adenocarcinoma (FIGHT)
• Abstract Number: 160
• Oral Abstract Session: Esophageal and Gastric Cancer
• Day and Time: Friday, January 15, 2021, 7:00am – 8:15am PST / 10:00am 11:15am EST
• Author and Q&A Presenter: Zev A. Wainberg, M.D., Associate Professor of Medicine at UCLA, Co-director of the Gastrointestinal Oncology Program and Director of Early Phase Clinical Research at the Jonsson Comprehensive Cancer Center

Conference Call Information

Five Prime will host a conference call and live audio webcast on Friday, January 15, 2021 at 4:30pm EST / 1:30pm PST to discuss the detailed Phase 2 FIGHT trial results presented at ASCO GI. To participate in the conference call, please dial (877) 878-2269 (domestic) or (253) 237-1188 (international) and refer to conference ID: 2063209. To access the live webcast please visit https://investor.fiveprime.com/events-presentations.

An archived copy of the webcast will be available on Five Prime's website beginning approximately two hours after the conference call. Five Prime will maintain an archived replay of the webcast on its website for at least 30 days after the conference call.

About the FIGHT Trial

The FGFR2b Inhibition in Gastric and Gastroesophageal Junction Cancer Treatment (FIGHT) trial (NCT03694522) was designed to evaluate the efficacy and safety of bemarituzumab in combination with modified FOLFOX6 (mFOLFOX6; leucovorin calcium, fluorouracil, and oxaliplatin) vs. mFOLFOX6 plus placebo in the front-line setting of patients with newly diagnosed FGFR2b positive, locally advanced or metastatic gastric and GEJ cancer.

Patients’ tumors were identified to be FGFR2b+ by immunohistochemistry and by FGFR2 gene amplification using a blood-based circulating tumor DNA assay. Testing was performed at a central laboratory.

The trial enrolled 155 patients in 15 countries across Asia, the European Union, and the United States.

About FGFR2b

The fibroblast growth factor (FGF)/fibroblast growth factor receptor (FGFR) pathway is implicated in the development and growth of cancer cells. FGFR2b is a form of FGFR found in epithelial cells, such as those in the stomach and skin. Data from the FIGHT trial suggests that approximately 30% of patients with non HER2+ gastroesophageal cancers overexpress FGFR2b.1 Five Prime and Roche Tissue Diagnostics have also found that FGFR2b is overexpressed in numerous other cancers, including squamous non-small cell lung cancer (NSCLC), triple negative breast (TNBC), ovarian, pancreatic and intrahepatic cholangiocarcinoma.

About Bemarituzumab

Bemarituzumab (anti-FGFR2b, FPA144) is a first-in-class targeted antibody that blocks fibroblast growth factors (FGFs) from binding and activating FGFR2b, inhibiting several downstream pathways. Blocking FGFR2b activation is thought to slow cancer progression. Bemarituzumab is being developed in gastric and GEJ cancer as a targeted therapy for tumors that overexpress FGFR2b.

Five Prime granted an exclusive license to Zai Lab to develop and commercialize bemarituzumab in Greater China, and Zai Lab collaborated with Five Prime on the Phase 2 FIGHT trial in Greater China.

About Gastric Cancer and GEJ Cancer

Gastric cancer, also known as stomach cancer, is the third most common cause of cancer death worldwide and, excluding non-melanoma skin cancer, the fifth most common cancer worldwide, with over 1,000,000 new cases diagnosed each year.2 For HER2- patients, front-line therapy available today is the same systemic chemotherapy available since the 1990s.3,4

About Five Prime Therapeutics

Five Prime is a clinical stage biotechnology company relentlessly focused on rewriting the narrative for people with cancer. By tackling the tough scientific questions and untapped pathways, we aim to offer new hope by developing novel, breakthrough therapies that have potential to alter the course of disease in cancers with few treatment options. This vision is what defines us, and guides our research, clinical development and partnerships. To build a better tomorrow for people with cancer, we are teaming up with patients, physicians, scientists, and industry partners to make a meaningful difference in patients’ lives. Five Prime collaborates with leading global pharmaceutical companies and has therapies in pre-clinical and clinical development. For more information, please visit www.fiveprime.com.

Cautionary Note on Forward-looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Words such as "may," "will," "expect," "plan," "anticipate," "estimate," "intend" and similar expressions (as well as other words or expressions referencing future events, conditions or circumstances) are intended to identify forward-looking statements. These forward-looking statements are based on Five Prime's expectations and assumptions as of the date of this press release. Each of these forward-looking statements involves risks and uncertainties. Forward-looking statements contained in this press release include statements regarding (i) the potential advancement of the development of bemarituzumab; (ii) the potential use of bemarituzumab, including in combination with other products, to treat patients; (iii) the potential development of bemarituzumab in indications in addition to gastric and GEJ cancer; (iv) the timing of the presentation of data for bemarituzumab; and (v) the extent of FGFR2b protein overexpression in certain patient populations. Actual results may differ materially from these forward-looking statements. Many factors may cause differences between current expectations and actual results, including unexpected safety or efficacy data observed during research, preclinical or clinical studies, changes in expected or existing competition, changes in the regulatory, pricing or reimbursement environment, and unexpected litigation or other disputes. In addition, while the company expects the COVID-19 pandemic to adversely affect its business operations and financial results, the extent of the impact on the company’s ability to advance its preclinical development and business and corporate development and other objectives will depend on future developments that are highly uncertain, and the company cannot predict with confidence the ultimate duration of the pandemic, travel restrictions, quarantines, social distancing and business closure requirements in the U.S. and in other countries and the effectiveness of actions taken globally to contain and treat COVID-19. Other factors that may cause actual results to differ from those expressed or implied in the forward-looking statements in this press release are discussed in Five Prime’s filings with the U.S. Securities and Exchange Commission, including the “Risk Factors” contained therein. Except as required by law, Five Prime assumes no obligation to update any forward-looking statements contained herein to reflect any change in expectations, even as new information becomes available.

References

1. Data on file. Five Prime Therapeutics; 2020.

2. Bray F, Ferlay J, Soerjomataram I, et al: Global cancer statistics 2018: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA Cancer J Clin. 2018;68(6):394-424. doi:10.3322/caac.21492

3. Wagner AD, Syn NL, Moehler M, et al. Chemotherapy for advanced gastric cancer. Cochrane Database Syst Rev. 2017;8(8):CD004064. doi:10.1002/14651858.CD004064.pub4

4. Drugs approved for stomach (gastric) cancer. Food and Drug Administration. Updated April 21, 2020. Accessed October 14, 2020. https://www.cancer.gov/about-cancer/treatment/drugs/stomach#1

Source: Five Prime Therapeutics, Inc.

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