The makers of the once-promising experimental mesothelioma drug defactinib have announced that they will stop a clinical trial of the drug early because, by itself, it does not appear to help. But this may not be the end of the road for defactinib in mesothelioma treatment.
Defactinib (VS-6063) had been the leading compound for its manufacturer, Boston-based Verastem. While standard mesothelioma chemotherapy drugs like pemetrexed, cisplatin, gemcitabine and vinorelbine can sometimes shrink mesothelioma tumors, they also increase the percentage of stem cells which can give rise to new cancer. Defactinib was designed to help keep malignant mesothelioma patients from relapsing by inhibiting a crucial signaling pathway (FAK) inside the stem cells.
Early studies were encouraging, but a recent review of the data determined that defactinib was not effective enough to justify continuing to test it on mesothelioma patients. “With the aggressiveness of this disease, the use of single agent VS-6063 as a maintenance treatment following chemotherapy where all patients had residual disease was not sufficient,” explains Verastem Chief Medical Officer Lou Vaickus, MD.
Verastem CEO Robert Forrester said the company would redirect its resources from the current trial into other studies of defactinib and two other possible mesothelioma drugs called VS-4718 and VS-5584, both of which are also FAK-inhibitors. VS-5584 was granted Orphan Drug status this past February. The company says there is evidence that VS-5584 and defactinib may work synergistically to destroy mesothelioma tumors in relapsed patients. A Phase 1 study is ongoing.
Malignant mesothelioma is the rarest and most deadly of the illnesses associated with asbestos exposure. According to the CDC there are 2,500 new cases diagnosed in the US each year. Conventional cancer treatments have done little to improve the prognosis for mesothelioma patients, which is usually poor.
“Verastem Stops Enrollment Due to Futility in the COMMAND Study of VS-6063 for the Treatment of Malignant Pleural Mesothelioma”, Company Statement, Verastem website, September 28, 2015
“A Phase 1 Dose Escalation Study of VS-5584 Administered in Combination With VS-6063, in Subjects With Relapsed Malignant Mesothelioma”, Government Clinical Trial website.