Five Prime Therapeutics, Inc. announced preliminary data from Part 1 of the ongoing Phase 1 clinical trial of FPA144 in patients with solid tumors, including gastric cancer, at a poster presentation at the American Society of Clinical Oncology's (ASCO) 2016 Gastrointestinal Cancers Symposium in San Francisco. FPA144 Phase 1 Safety and Pharmacokinetic Summary: Safety data from 27 patients and pharmacokinetic (PK) data from 23 patients from Part 1a (3+3 dose escalation in solid tumor patients) and Part 1b (parallel escalating doses in gastric cancer patients); FPA144 was well tolerated in patients with advanced solid tumors up to 15 mg/kg; No dose-limiting toxicities (DLTs) were observed and a maximum-tolerated dose (MTD) was not reached in Part 1; The most common treatment-emergent adverse events were Grades 1 or 2 and self-limiting; The safety profile appears differentiated from small molecule kinase inhibitors targeting FGF receptors; for example, no treatment-related hyperphosphatemia was observed; The most common treatment-related adverse events were: fatigue (25.9%), nausea (11.1%), diarrhea (7.4%), dizziness (7.4%)and dry eye (7.4%); PK characteristics support once every other week or less frequent dosing. Preliminary Data on Anti-tumor Activity: Anti-tumor activity in patients with gastric cancer whose tumors overexpress the FGFR2b protein (the initial target patient population for FPA144): First radiographic assessment by RECIST 1.1 of anti-tumor activity in six patients with FGFR2b-positive gastric cancer in Part 1b; 2 Partial Responses (1 confirmed who received 6 mg/kg, 1 unconfirmed who received 10 mg/kg); 3 Stable Disease (2 confirmed who received 3 mg/kg and 10 mg/kg, respectively; 1 unconfirmed who received 10 mg/kg); 1 Progressive Disease (who received 10 mg/kg); Patients were classified 3+ by an IHC molecular diagnostic test.

Anti-tumor activity in a patient with urothelial bladder cancer: A confirmed Partial Response by CT (RECIST 1.1) and metabolic response by PET was observed in a urothelial bladder cancer patient who received 3 mg/kg from Part 1a; The patient's tumor was classified 2+ by an IHC molecular diagnostic test, suggesting that FPA144 may be active in tumors with moderate levels of FGFR2b protein overexpression; Encourages investigation of the potential for FPA144 therapy in tumor types other than gastric cancer. All patients who showed anti-tumor activity received doses below the 15 mg/kg dose being assessed in Part 2 of the trial.