KRAS biotech Mirati delivers so-so news for investors closely watching Amgen battle

Mirati Therapeutics investors waiting to hear the latest in the KRAS inhibitor story were disappointed Thursday evening, as the biotech reported that a few key clinical developments have slipped to 2022.

Hot on Amgen's heels in the race to bring a KRAS-inhibiting cancer drug to market, Mirati said Thursday that most of its clinical programs for adagrasib are on track, including solo studies in non-small cell lung cancer and two colorectal cancer studies.

However, Mirati had been expecting additional data this year from a phase 1/2 study of adagrasib, which targets G12C mutations, combined with Novartis’ experimental SHP-2 inhibitor. That's now been pushed to the first quarter of 2022.

Mirati will hold off on launching a clinical trial of MRTX1133, a second KRAS inhibitor that targets G12D mutations, until next year. The candidate was previously expected to be a traditional oral or IV formulation, but Mirati has pivoted to a long-acting formulation that will require fewer infusions.

RELATED: Amgen's up-and-coming KRAS inhibitor gets a name: Lumakras

The company’s shares dipped more than 10% around noon as investors reacted to the so-so news. 

“While these delays may be poorly received by some investors, we believe that there remain several significant data readouts this year that could drive additional upside,” SVB Leerink said in a note.

The delay could stem from the FDA’s decision to impose a post-marketing trial requirement on Amgen—Mirati’s chief rival in the KRAS arena, SVB Leerink said. In late April, the agency asked Amgen to study a lower dose of Lumakras, the KRAS inhibitor previously known as sotorasib. This could signal that the FDA has concerns about the safety of these emerging treatments.

Mirati told investors during the earnings call that the FDA has not requested a similar study for its KRAS program. And the company is already conducting several clinical trials examining different doses, which were kicked off without prodding from the agency, SVB Leerink said.

Amgen, too, had a trial in the hopper studying a lower dose, putting them in a good position to respond to the FDA's request. 

RELATED: Mirati's KRAS drug shrinks 45% of NSCLC tumors, putting it in Amgen's slipstream on race to FDA

Amgen will likely be the first company to reach the KRAS market as Lumakras is set for an August decision from the FDA on its first indication in non-small cell lung cancer. 

But Mirati is close behind, with an expected FDA filing for adagrasib’s first new drug application in the second half of this year in the same indication.

"Mirati continues to advance an innovative pipeline of drug candidates,” said Mirati President and CEO Charles Baum in a statement. “The company expects to file IND applications for two potentially first-in-class therapies—our KRAS G12D inhibitor, MRTX1133, in 2022, and a synthetic lethal MTA cooperative PRMT5 inhibitor, in the first half of 2022."