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Purpose Alofanib is a small-molecule allosteric extracellular FGFR2 inhibitor. We report safety and preliminary efficacy from the first-in-human phase 1b study of alofanib in heavily pretreated patients with advanced gastric cancer. Methods The standard dose-escalation design 3 + 3 aimed to establish the maximum tolerated dose (MTD) or recommended phase 2 dose (RP2D). Alofanib was administered daily intravenously 5 days on, 2 days off. There were five dose levels (50–350 mg/m2). All patients received alofanib until disease progression or unacceptable toxicity. Results 21 patients were enrolled. Patients were predominantly male (71%), 67% had 2 and more metastatic sites, including liver metastases (43%), 19% had ECOG PS 2, and were heavily pretreated (86% had previous 2 and more treatment lines). During dose escalation, no dose-limiting toxicities were observed, and MTD was not defined. 15 (71.4%) patients had at least one adverse event associated with the treatment (TRAE). Grade 3 or higher TRAEs were observed in 6 patients (28.6%). The most common TRAEs included reactions immediately after administration, diarrhea, thrombocytopenia, arthralgia, and headache. The median progression-free survival and overall survival was 3.63 (95% CI 1.58–5.68) and 7.0 (95% CI 3.82–10.18) months, respectively. The 6- and 12-month overall survival rates were 57.1% and 33.3%. Disease control rate was 68% with one durable partial response. Conclusions The MTD has not been reached and dose of 350 mg/m2, 5 days on, 2 days off has been declared as RP2D. Alofanib showed acceptable tolerability and preliminary signs of clinical activity in the late-line treatment of metastatic gastric cancer. ClinicalTrials.gov identifier: NCT04071184

Alofanib is a potent, small molecule, allosteric inhibitor that binds to the non-active extracellular site of IIIc and IIIb FGFR2 isoforms. Phase 1b clinical study (RPT835GC1B) met its primary endpoints and recommended phase 2 dose was described early. Here, we present pharmacokinetics (PK) and results of biomarker analysis. Alofanib was administered daily intravenously for 5-days followed by a 2-day interval (rest). There were five dose levels using a 3 + 3 design. 21 patients have been enrolled in the study. Patients were Caucasian (100%), predominantly male (71%), 67% had 2 and more metastatic sites, including liver (43%) and bone (14.3%) metastases, 19% had ECOG PS 2, and were heavily pretreated (86% had previous 3 and more lines of therapy). The PK and biomarker analysis set included 18 patients. FGFR2 amplification was accessed by FISH with ZytoLight SPEC FGFR2/CEN 10 Dual Color Probe and FGFR2 expression was accessed by IHC with antibody 1G3 (Abcam (ab 5820). Table summarizes PK data. The geometric mean values of Cmax, AUC0-t, T1/2, Vd increased and CL, Kel decreased approximately dose-proportionally after single dosing, similar to previous preclinical studies. The decrease in the mean value of the Vd for a dose of 350 mg/m2 may be associated with a significant increase in AUC0-t. No correlations between PK values and objective response rate (n=2; 9.5%), progression-free (median 3.63 months (95% CI, 1.58 - 5.68) and overall (median 7.0 months (3.82 - 10.18) survival as well as in patients with liver metastases were found (all P>0.1). A positive FGFR2 IHC expression was observed in all tumor cells and a weak positive reaction in normal epithelium. FGFR2 amplification was confirmed by FISH in 1 (5.6%) patient.Alofanib PK in a gastric patient population is well characterized, supporting the use of a once-daily 350 mg/m2 dose. In further studies, the evaluation of FGFR2 amplification seems to be important. Cohort 1 Cohort 2 Cohort 3 Cohort 4 Cohort 5 50 mg/m2 100 mg/m2 165 mg/m2 250 mg/m2 350 mg/m2 Cmax, mcg/ml (CV%) 21.4 (32.3) 23.7 (18.4) 44.7 (15.5) 72.8 (64.3) 145.9 (42.7) AUC0-t, mcg*h/ml (CV%) 2.3 (31.9) 6.6 (14.2) 13.3 (49.9) 23.8 (8.7) 74.0 (57.5) Vd, ml/m2 (CV%) 4006.1 (28.3) 4907.5 (14.7) 5676.8 (26.6) 6686.7 (11) 3823.0 (63.8) CL, ml/h/m2 (SD) 19609.5 (7740) 14028.2 (1990) 11910.5 (8740) 10011.0 (827) 4183.0 (2420) Kel, 1/h (CV%) 4.9 (15.3) 2.9 (2.8) 2.1 (41.2) 1.5 (3.8) 1.1 (47.0) T1/2, h (SD) 0.1 (0.024) 0.2 (0.01) 0.3 (0.118) 0.5 (0.0171) 0.6 (0.293) Citation Format: Grigory Raskin, Vasily Kazey, Svetlana Gorbacheva, Aiyyna Nikiforova, Galina Statsenko, Elena Artamonova, Liubov Vladimirova, Natalia Besova, Anastasia Mochalova, Ivan Rykov, Vladimir Moiseyenko, Igor Utyashev, Sergei Iugai, Nadezhda Dragun, Dmitry Reznikov, Evgenia Gavrilova, Sergei Tjulandin, Ilya Tsimafeyeu. Pharmacokinetics of alofanib and biomarker analysis in patients with advanced gastric cancer: A phase 1b study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3481.