Mirati seems to have gotten what it needed in terms of efficacy for its KRAS inhibitor, notching an objective response rate of 43% in non-small cell lung cancer, compared to Amgen’s 37% for its already approved med Lumakras.
But the problem lies with how long the effect lasts. On that measure, Amgen appears to have taken the win.
Mirati will show off some new cohort data from the phase 2 KRYSTAL-1 study of adagrasib at the 2022 American Society of Clinical Oncology (ASCO) conference in June, with a peek at the data posted Thursday evening.
The mixed data drop, the latest in a neck-in-neck race between the two companies, sent Mirati’s shares plummeting 32% in premarket trading to $39.73, compared to $58.46 at close Thursday.
Amgen won the race to the market, getting Lumakras approved in lung cancer last spring. But Mirati has always had a shot at making up ground if it could put up better efficacy or durability data. Today, those hopes seem to be fading.
The new data are from 116 patients, the majority of whom had prior treatment with a PD-1/L1 inhibitor after chemotherapy, at 12.9 months after treatment in the trial. The ORR was 43%, and the disease control rate was 80%, Mirati said. The median duration of response was 8.5 months while median progression free survival was 6.5 months.
Lumakras, on the other hand, recorded a lower objective response rate in data released at last year’s ASCO conference from a similar population of 124 patients who had previously received both platinum-based chemotherapy and immunotherapy. But the duration of response for Lumakras was more than two and a half months longer than adagrasib at 11.1 months. The disease control rate was the same at 80%.
On overall survival, adagrasib recorded 12.6 months as of the Jan. 15 data cutoff, just barely beating Lumakras’ 12.5 months.
Adagrasib is being considered by the FDA, with a decision date expected in mid-December. That puts Mirati—which had been hoping for a regulatory decision in the second quarter—about 19 months behind Amgen. The news that the decision would come at the end of the year sent Mirati’s shares below $100 apiece. That decline has continued to the sub-$40 value today.