Amgen Slips as Gene-Targeting Drug Misses Some ‘Lofty Hopes’

(Bloomberg) -- More than half of patients with an advanced form of lung cancer initially responded to an experimental drug from Amgen Inc. that targets a genetic driver of the disease previously considered impervious to treatment. The stock fell as the drug failed to impress investors.

The highest dose of Amgen’s AMG 510 shrank tumors in seven of 13 patients and the disease was stable in the remaining six, though the benefit didn’t always last. Nine remain in the study and are still taking the daily pill. One patient’s cancer progressed after initially responding to treatment, while three others subsequently died, according to results presented at the World Conference on Lung Cancer in Barcelona.

The findings show researchers may have identified a way to counter KRAS, a common gene in human tumors. The form of the gene targeted by AMG 510 occurs in about 13% of non-small cell lung cancers. Previously, finding a KRAS mutation could only be used to rule out treatment.

“If we can expand this and show in a large body of patients that we have response rates on the order of 50% or somewhere near that, that is very clinically relevant and meaningful,” said Dave Reese, Amgen’s head of research and development. “It’s early days. We need to see if some of these responses will deepen over time.”

Amgen’s results are the first in patients for a KRAS inhibitor focused on a mutation known as G12C, putting it in the lead against rivals such as Mirati Therapeutics Inc. and Johnson & Johnson. The findings, while positive, open the door for competing drugs that may work better or last longer. Lung cancer kills 142,000 Americans a year.

Amgen’s stock slid 2.5% to $202.47 at 10:35 a.m. in New York. The data “continue to look strong, if not fully up to lofty hopes,” RW Baird analyst Brian Skorney wrote in a note to clients. Mirati shares rose 6.9%.

The U.S. Food and Drug Administration granted AMG 510 fast-track status for patients with metastatic non-small cell lung cancer with the G12C mutation. Amgen is beginning its next study, which may be used to get approval of the drug, Reese said.

Right Direction

The findings follow data this summer that showed half of those treated with Amgen’s drug at a wide range of doses responded. The latest results more than doubled the number of patients treated with the highest dose and tracked them for three more months. It’s too early to know how long the benefits will last and whether treatment prolongs patients’ lives.

For such very sick lung-cancer patients, any response rate above 35% would be viewed as an achievement, Jefferies analyst Michael Yee told investors in a note before the latest results.

“The higher the response, the tougher it is” for rivals like Mirati, he said. The small-cap’s shares have nearly doubled this year even though the company has yet to report any data for its KRAS-targeting molecule.

The Amgen results are a clear breakthrough, said Channing Der, professor at the Lineberger Comprehensive Cancer Center at the University of North Carolina Chapel Hill. Previous efforts showed promise in the laboratory, and then failed to deliver, he said.

“This tells us we are heading in the right direction and that this concept is the right one,” said Der, who has worked for decades on KRAS and similar mutations and serves on Mirati’s scientific advisory board. “It’s far from saying we are done. The cautious sentiment in the field is that these inhibitors will be successful, but what percent will actually respond to this treatment and for how long is unknown.”

It’s critical to know how long the patients will benefit from treatment, he said. There is a history of cancer treatments shrinking tumors but failing to help patients live longer, he said. “At the end of the day, if you don’t get an impact on survival, it’s not considered a success,” he said.

Enduring Responses

All of the patients in the Amgen study were battling lung cancer that had already worsened despite having received an average of more than three types of treatment, including standard chemotherapy and immunotherapy.

Of the 23 patients with non-small cell lung cancer who were given AMG 510, 11 posted an initial response to treatment and eight continue to benefit from it. One who got the lowest dose is still responding after 42 weeks of treatment, while another who got an intermediate dose has had a near complete response that has carried on through 30 weeks.

“About 50% of the patients seem to be having responses, and that number seems to be durable,” said Greg Friberg, head of oncology at Amgen. “We are quite hopeful that these results are going to continue to be consistent over time.”

The medicine appeared safe with no toxicities to limit dosing and no drug-related side effects that would cause patients to stop treatment. Three of 34 lung cancer patients enrolled in the study experienced anemia or diarrhea. None had life-threatening conditions tied to the drug.

To contact the reporters on this story: Michelle Fay Cortez in Minneapolis at mcortez@bloomberg.net;Cristin Flanagan in New York at cflanagan1@bloomberg.net

To contact the editors responsible for this story: Drew Armstrong at darmstrong17@bloomberg.net, Timothy Annett, Mark Schoifet

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