Esmo IO – Mirati struggles to keep the first-line dream alive

When it comes to adagrasib's chances in the potentially lucrative first-line lung cancer setting, Mirati still has some convincing to do. Amgen set a low bar earlier this year at World Lung: adding its rival Kras inhibitor, Lumakras, to checkpoint inhibition came with worrying levels of liver toxicity and a meagre 29% overall response rate. Standard-of-care Keytruda presents a much bigger challenge, and topline data in an abstract, released ahead of a full presentation at the Esmo Immuno-Oncology conference tomorrow, point to adagrasib coming up short. SVB analysts described a 49% ORR for adagrasib plus Keytruda as “relatively modest” and in-line with Keynote-189, which tested the Merck & Co MAb plus chemo. Adagrasib needs to do much better for any hope of justifying front-line usage; Stifel analysts described a 56% ORR generated in six patients treated for more than six months as “trending in the right direction”. Responses stratified by patients’ PD-L1 expression levels will be scrutinised tomorrow, and perhaps point to a way forward. Mirati plans to launch a phase 3 trial in patients with low PD-L1 expression “soon”, according to Reuters. But with Mirati shares opening down 17%, it seems the market was expecting a lot more.