Amgen tosses back unwanted bispecific to Xencor as KRAS data on track for 2020 readout

Amgen's Gateway of Pacific building in South San Francisco (Business Wire)

Amgen has culled a bispecific drug it picked up in a $1.7 billion biobucks deal with Xencor.  

In its second-quarter results, the biopharma said: “Phase 1 development of AMG 424, a CD38-CD3 XmAb antibody has been stopped, with rights reverting to Xencor.”

Amgen nabbed the preclinical asset back in 2015 as part of an early-stage, bispecific six-drug development deal with Xencor. Under the deal, Amgen paid just $45 million upfront to use its R&D tech on some preclinical antibodies designed to harness the body's natural defenses.

The pact was worth up to $1.7 billion in biobucks.

Xencor had been the biotech partner of choice for a number of Big Pharmas but was beginning to fall out of favor. In January last year, Novartis also returned the rights to a bispecific antibody it had licensed as part of a 2016 deal worth up to $2.41 billion.

A few months down the line, and the biotech was hit again after a second asset from that deal, in development for acute myeloid leukemia, hit a snag in the form of a partial clinical hold from the FDA. This came after a failed phase 2 test in lupus for the company in 2018.

But things had started to turn around: After working with Xencor to change the study protocol, the FDA lifted the partial clinical hold April 30.

And although Xencor lost Novartis as a partner on one of its programs, it picked up a new partner, licensing its preclinical-stage IL-15 cytokine therapeutics to Genentech for $120 million upfront in February last year.

Since then, Xencor has inked an R&D deal with Astellas and started phase 1 studies for two more bispecific antibodies in advanced solid tumors: XmAb2314, which targets PD-1 and ICOS, and XmAb22841, which targets CTLA-4 and LAG-3. The latter treatment is being tested in combination with Keytruda in an effort to block three checkpoints at once.

But the Amgen cull was still a hard hit for the biotech in the short term, with its shares off nearly 5% after-hours Tuesday on the news.

Meanwhile, one of the most keenly watched cancer drugs in development, KRAS drug AMG 510 (now known as sotorasib) is still on track to deliver data from a potentially pivotal phase 2 monotherapy study in patients with advanced non-small cell lung cancer (NSCLC) in the coming months, despite ongoing pandemic disruptions to trials.

Amgen also noted its phase 3 CodeBreaK 200 study comparing sotorasib to docetaxel is also now “enrolling patients with advanced NSCLC,” while it has six phase 1 combination cohorts also enrolling.

Sales for Amgen grew 6% to $6.2 billion for the second quarter.