ESMO: With Mirati hot on its tail, Amgen's KRAS-targeting Lumakras combo heads into late-stage colorectal cancer testing

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The results for the combo therapy were “much higher” than the 9.7% response Lumakras managed to generate alone, said David Reese, M.D., executive vice president of research and development at Amgen. (Amgen Inc)

Amgen made history earlier this year when it pedaled Lumakras over the FDA’s finish line in lung cancer, making it the first med to target the “undruggable” KRAS mutation. Now, the company is trying to back up that win with another in colorectal cancer, and it’s touting early-stage data that could help it get there. 

In a phase 1b/2 study dubbed CodeBreak 101, a combination of Amgen’s KRAS inhibitor Lumakras and its EGFR inhibitor Vectibix showed “encouraging” effectiveness and safety results in patients with KRAS G12C-mutated colorectal cancer (CRC).

With the promising early data in hand, the company plans to launch a phase 3 trial for the combo in the third-line setting, said David Reese, M.D., executive vice president of research and development at Amgen. 

In all, the early trial enrolled 31 patients who were heavily pretreated—having had a median of two prior therapies—in its dose exploration and dose expansion cohorts for the Lumakras-Vectibix combo. 

Specifically, the meds triggered a response in 27% among the 26 patients in an efficacy analysis group, which included five patients whose disease progressed after previous treatment with Lumakras as a solo therapy, Amgen reported. The results for the combo therapy were “much higher” than the 9.7% response Lumakras managed to generate alone, Reese said. 

Overall, the disease control rate for the combo came in at 81%. In a cohort of 18 patients with stubborn colorectal cancer who had never been treated with Lumakras, the combo therapy was tied to a 33% response rate, Amgen said. 

RELATED: Surprise! Amgen's hot KRAS drug seals early FDA approval, winning a shot against 'undruggable' cancer

The California-based drugmaker plans to share the data at the upcoming European Society of Medical Oncology 2021 (ESMO21) Virtual Congress over the weekend. 

To Amgen, there’s a high need for additional treatment options for patients with previously treated colorectal cancer that’s spread. The median progression-free survival time for those patients stands at just two months and response to current treatments can be as low as 2%, the company said. 

Colorectal cancer diagnoses comprise 10% of all cancer diagnoses globally. While Amgen’s early-phase data looks “encouraging,” the KRAS G12C mutations occur in no more than 5% of CRC patients, Jefferies analysts pointed out in a note to clients on Thursday following the release. 

That means Amgen’s prospects in colorectal cancer will likely be a fraction of its potential in lung cancer, where upwards of 13% of those patients carry the key KRAS mutation, the analysts said. Jefferies expects peak combo sales in the “few hundred million” for colorectal cancer. 

RELATED: Amgen's KRAS rival Mirati gets a shot in the arm with breakthrough tag for follow-on therapy

That could be cut down even further if Mirati Therapeutics manages to cross its own KRAS-targeting med over the FDA’s finish line, Jefferies said. The company could launch its inhibitor adagrasib, which has fallen over a year behind Lumakras but could prove superior by the end of next year, according to the note.