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

Mirati Therapeutics may not have crossed the finish line first in the KRAS inhibitor race—that trophy was claimed by Amgen last month—but the biotech is hoping a breakthrough tag for its follow-on therapy will boost the chances of a silver medal.

The San Diego biotech was granted the FDA designation Thursday for adagrasib, a KRAS-inhibiting drug that targets G12C mutations in patients with non-small cell lung cancer (NSCLC).

Mirati's shares reached $170 early in trading hours Friday but returned to less than 1% above the prior day's close near $163 around noon. 

Amgen received the nod for Lumakras well ahead of an expected August decision date, putting pep in the pharma's step. About six months passed from the time Lumakras, formerly known as sotorasib, received a breakthrough therapy designation to the eventual approval.

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Preliminary results from a registrational phase 1/2 trial in NSCLC patients who had previously undergone immunotherapy and/or chemotherapy were what gave the FDA confidence, Mirati said.

Mirati CEO and President Charles Baum, M.D., Ph.D., said in a statement the company is "pleased" with the designation and will submit for regulatory approval in the second half of this year. 

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Mirati is trying to go head to head with Amgen, which developed Lumakras in just eight years, for a disease that affected 2.21 million people globally last year. G12C is the most common KRAS mutation, at about 14% of patients, according to Mirati. 

Amgen, for its part, believes Lumakras is slightly different than Mirati's offering, so there could be room on the market for both therapies. 

Addressing the competition in an interview with Fierce Biotech last month, Amgen's Greg Friberg said, “It's good for there to be multiple opportunities to prosecute a given Achilles heel tumor." Friberg is Amgen's vice president and therapeutic area head, oncology. 

Adagrasib, an oral small molecule, is shown to have a long half-life, is well tolerated and leads to extensive tissue distribution, Mirati said. 

The breakthrough therapy tag is a welcome boost for Mirati, which saw shares dip last month after announcing delays to some key programs for adagrasib. Most of the programs are on track, but the company revealed that additional data from a phase 1/2 study of the drug in combination with Novartis' experimental SHP-2 inhibitor was pushed back to the first quarter of next year.

Mirati will also hold off on launching a clinical trial for a second KRAS inhibitor that targets G12D mutations until 2022 after pivoting to a long-acting formulation rather than a traditional oral or IV one.