For a moment, Verastem Oncology looked like one of the early winners of the American Society of Clinical Oncology’s annual meeting.
The company’s shares $VSTM were trading up over 50% after hours based on Thursday’s promising early results from its targeted drug combination in pancreatic cancer, a devastating and often fatal disease. Five of six pancreatic cancer patients in the first cohort of an early-stage trial saw their tumors shrink more than 30% after receiving Verastem’s treatment.
But Friday morning, Verastem’s stock tanked by about 60% to less than $5 a share after the company announced that it’s filing its lead program for accelerated approval in a much smaller population of ovarian cancer patients than previously expected.
In a securities filing, updated results from a Phase 2 study showed that the percentage of ovarian cancer patients who responded to its therapy fell to 27% from the 45% that Verastem touted last year in a much earlier cut of the data. The new results featured 109 patients and a cutoff in February. Last year’s efficacy analysis included 29 patients.
Verastem is developing drug combinations featuring avutometinib and defactinib for a number of cancers, including ovarian, pancreatic, lung and other gynecological cancers. Avutometinib and defactinib are both inhibitors that target key cancer-driving pathways. In particular, avutometinib targets the RAS pathway, where gene mutations drive a large portion of cancers.
The company is hoping the combination will win accelerated approval in low-grade serous ovarian cancer, a rare form of a slow-growing chronic cancer that doesn’t have many treatment options. But after discussions with the FDA, it’s now filing for accelerated approval only in a subgroup of low-grade serous ovarian cancer patients with KRAS mutations — and excluding those without KRAS mutations. However, Verastem management noted on an investor call that the FDA could expand the indication in a future review of the ovarian cancer data.
Dan PatersonThe updated Phase 2 results may explain why. Roughly half of the patients in the analysis had KRAS mutations, while half did not. The response rate in those with KRAS-mutated cancer was 37%, but the response rate in those with no KRAS mutation was just 15%.
Verastem CEO Dan Paterson said in a press statement that the company expects to complete its application for FDA approval later this year and it plans to discuss with regulators how to move forward in patients without KRAS mutations. The company also expects to share mature data from the Phase 2 ovarian cancer study at a medical meeting later this year.