The negative market reaction came as Agenus revealed outcomes of its end-of-Phase II meeting with the FDA, where the agency advised against submitting recent trial results in a bid to secure a speedy approval for the regimen. The FDA's stance was based on the view that the objective response rates (ORRs) observed may not necessarily translate to a survival benefit. Topline interim data from the ongoing Phase II trial showed trends consistent with earlier Phase I results, according to the company. In the cohort receiving the agreed-upon Phase III dose (BOT 75 mg/BAL 240 mg), Agenus said the ORR was 19.4% after a median 9.5 months of follow-up, with a six-month survival rate 90% and data continuing to mature. At the increased BOT dose of 150 mg, the combination was associated with an 8.2% ORR. Results of a 77-patient Phase I study reported earlier this year, had shown a 23% ORR with the regimen after a median follow-up of 13.6 months. The estimated median overall survival was 21.2 months. Like the Phase II trial, the earlier study also included refractory MSS CRC patients with no active liver metastases. Steven O'Day, the company's chief medical officer, indicated Thursday that Agenus was still committed to the programme despite the regulatory hurdle. "Based on the high level of enthusiasm from significant numbers of global clinical experts and the promising clinical activity we have seen in the Phase I and II studies, our commitment to seek all possible pathways to make BOT/BAL available to patients is unwavering," O'Day stated, adding "this includes exploring opportunities to partner in the US to accomplish a successful Phase III trial."
The company noted that FDA has recommended the inclusion of a BOT monotherapy arm "at Agenus' discretion" in the Phase III study. The toplined mid-stage results unveiled Tuesday showed an ORR of 7.5% for BOT monotherapy at 150 mg, but no response at the 75-mg dose. In the meantime, Agenus says it is ploughing ahead with efforts to bring BOT/BAL to patients in Europe, where discussions to explore registration paths are scheduled for later this summer.