Amgen data supports KRAS cancer drug, but survival benefit remains in question

Full details from a late-stage study of Amgen’s KRAS-blocking drug confirm its effectiveness over standard chemotherapy in treating lung cancer, but fall short of proving that benefit translates into patients living longer. 

The results, released over the weekend and on Monday, show that treatment with Amgen’s drug, called Lumakras, reduced the risk of tumor growth or death by 34% compared to chemotherapy in patients with a certain kind of non-small cell lung cancer. 

On that measure, known as progression-free survival, study participants given Lumakras went a median of 5.6 months without disease progression or dying, versus 4.5 months for patients in the trial who received the chemotherapy docetaxel. More than twice as many Lumakras-treated patients responded to the drug as did those on chemo, according to the data. 

In late August, Amgen had said the study succeeded, but didn’t provide any specific data then. The full results were disclosed as part of the European Society for Medical Oncology’s annual conference in Paris, where they were presented Monday. 

The study’s outcome should help Amgen validate Lumakras’ accelerated approval in the U.S. last May, which was supported by data from a mid-stage study that did not compare the drug to other treatment. As a condition of that approval, Amgen is required to confirm its benefit via further testing.

Notably, however, the study data do not show that Lumakras helps patients live longer than does chemotherapy. Details in a presentation Monday indicated no benefit to Lumakras, with median overall survival among patients on Amgen’s drug reaching 10.6 months, versus 11.3 months for those given chemo.

The study was not designed, or “powered,” to compare survival between the two groups, Amgen noted. Additionally, about a third of those who initially received chemo went on to receive Lumakras or another targeted therapy like it. This kind of patient “crossover” in studies can sometimes distort results. 

Even so, the lack of a survival benefit is disappointment and could affect how doctors perceive Lumakras. While it’s the only drug of its type currently approved, others are being developed and one, from Mirati Therapeutics, is currently under review by the Food and Drug Administration with a decision expected by December. 

There were other shortfalls, too. The treatment response rate of 28% that researchers reported from the study is lower than the 36% included in Lumakras’ approved labeling, which was based on that earlier, single-arm study. 

While treatment with Lumakras was associated with fewer treatment-related side effects overall as well as fewer serious treatment-related adverse reactions, the drug more commonly led to diarrhea and liver enzyme elevations than chemotherapy. Liver toxicity has also cropped up as a concern in testing of Lumakras with a type of cancer immunotherapy. 

Amgen’s study, called CodeBreak-200, enrolled 345 previously treated patients with non-small cell lung cancer that was either locally advanced, metastatic or not removable by surgery. Patients’ tumors had to test positive for a specific mutation in a gene called KRAS. Often mutated in lung, colorectal and pancreatic cancers, the KRAS gene has been a target for cancer researchers for decades, but until Lumakras no drug had been able to successfully target it. 

It’s an important drug for Amgen and its approval has helped catalyze similar drug development efforts across the industry. 

Amgen also released data Monday from an early trial of Lumakras combined with the drug Vectibix in KRAS-mutated metastatic colorectal cancer. 

Shares in Amgen fell by 3% in Monday morning trading. 

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