Synergistic activity of aflibercept (VEGF Trap) in combination with 5-fluorouracil and irinotecan in preclinical tumor models

A13 Aflibercept is a novel angiogenesis inhibitor currently in phase 3 clinical trials. It is a fusion protein of key domains of the human VEGF receptors (VEGFR1 and 2) and the Fc portion of a human IgG1. It neutralizes all isoforms of circulating VEGF-A, blocks angiogenesis and inhibits tumor growth in vivo (Kim E. et al, 2002; Holash J., 2002, AACR 2005, Proc ASCO, 2004). It also blocks P1GF, a factor involved in pathological angiogenesis (Persico MG et al 1999). Aflibercept is in clinical development in combination with standard chemotherapy in several indications including colorectal cancer. Preclinical studies were done to assess the antitumor efficacy of aflibercept in combination with two cytotoxic agents approved for treating colorectal cancer: 5-fluorouracil (5-FU), an anti-metabolite, and irinotecan (CPT-11), a topoisomerase I inhibitor. In three-arm studies, single agent cytotoxic, single agent afilbercept, and the combination were tested for dose response effects, up to the highest non-toxic dose (HNTD). This allowed for the determination of positive or negative interaction of aflibercept with respect to overall tolerance and efficacy. The key efficacy endpoint was the log cell kill value (log CK = tumor growth delay / 3.32 x tumor doubling time). Synergy was recorded when the combination was at least 1 log superior to the log CK of the best single agent at equitoxic dosages. The combination of aflibercept (SC twice weekly) with 5-FU (IV weekly) was evaluated following a 3-week treatment period in mice bearing early stage murine mammary adenocarcinoma MA13/C. In this model, aflibercept alone was as active as the HNTD of 5-FU (90 mg/kg/dose). The doses of aflibercept 10, 25 and 40 mg/kg/dose (highest dose tested - HDT) produced a log CK of 1.3, 1.5, 1.4, respectively. The HDT of the combination (aflibercept 40 mg/kg/dose plus 5-FU 90 mg/kg/dose) produced a 2.7 log CK indicating that the combination was synergistic. Synergy was also maintained at lower combination doses. Of interest, there was no overlap in host toxicity, as aflibercept HDT was safely combined with the HNTD of 5-FU. The combination of SC aflibercept with IV irinotecan was evaluated in mice bearing advanced stage human colon carcinoma HCT 116 (155 mg tumor burden). Each agent was administered on day 12, 15 and 18 post-tumor implantation. The HDT of aflibercept alone, 40 mg/kg/dose, was active with a 1.7 log CK. Lower dosages, 25 and 10 mg/kg/dose, retained activity with 1.7 and 1.3 log CK, respectively. The HNTD of irinotecan alone (12.5 mg/kg/dose) was active with a 1.8 log CK. The HNTD of the combination (aflibercept 40 mg/kg/dose and irinotecan 20.2 mg/kg/dose) was well tolerated. This combination was synergestic, improving tumor cell kill by more than 1 log compared to the activity of the best single agent (3.0 log CK). Synergistic antitumor activity was maintained even at doses below the HNTD. In conclusion, aflibercept is an active compound in preclinical mouse tumor models and displays synergy at several dose levels when combined with 5-fluorouracil or irinotecan. The results support the clinical investigation of aflibercept in combination with cytotoxics in clinical indications, such as colorectal cancer.