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AstraZeneca, Daiichi’s Enhertu steps into the FDA’s fast lane for new stomach cancer use

AstraZeneca and Daiichi Sankyo are rapidly gaining traction for their Enhertu in HER2-positive breast cancer. Next up? An early chance at expanding the blockbuster-to-be into a tough-to-treat tumor type.

The FDA has granted priority review to Enhertu’s application in HER2-positive, metastatic gastric or gastroesophageal junction cancer, with a decision date set for the first quarter of 2021, the two companies said Wednesday.

AZ and Daiichi’s application is based on data from the phase 2 Destiny-Gastric01 trial in a cohort of 188 patients from Japan and South Korea whose HER2-positive gastric cancer had progressed after at least two previous treatment regimens.

Enhertu shrank tumors in 51% of patients, compared with 14% of those treated with their physician’s choice of chemotherapy. The antibody-drug conjugate also helped patients live longer, slashing the risk of death by 41% compared with chemo, according to data published in The New England Journal of Medicine.

That showing made Enhertu the first HER2-directed drug to extend the lives of patients with previously treated HER2-positive gastric cancer patients. Previously, Roche’s HER2 antibody-drug conjugate Kadcyla failed to beat chemo at helping second-line patients live longer.

Now, AZ and Daiichi will have their sights fixed on Kadcyla, which grew sales by 37% year over year in the first nine months of 2020 to reach CHF 1.30 billion ($1.42 billion), mainly driven by post-surgery use in breast cancer. Both meds use trastuzumab, or Roche’s Herceptin, as their antibody component to seek out HER2-expressing tumors, but their toxic payloads and linkers are different.

Now, to set Enhertu apart, AZ and Daiichi are running a head-to-head trial pitting their med against Kadcyla in second-line breast cancer. 

Enhertu may even have opportunity beyond HER2-positive cancers. The drug triggered responses in some patients with HER2-low gastric cancer in two exploratory cohorts in the Destiny-Gastric01 trial, according to data presented at this year’s European Society of Medical Oncology virtual meeting in September.

“Enhertu preliminary activity in HER2-low gastric cancer may expand opportunities beyond HER2-positive malignancies,” SVB Leerink analyst Andrew Berens said in a note at the time.

Approved in late 2019 and launched first thing in 2020, Enhertu brought in $76 million in the first half of the year, as recorded by Daiichi Sankyo. It has already snagged about a one-third share of patients in third-line breast cancer, Dave Fredrickson, AstraZeneca’s oncology commercial chief, told investors during a conference call in July.

Beyond breast and gastric cancers, Enhertu also has an FDA breakthrough designation to treat patients with metastatic HER2-mutated non-small cell lung cancer after progression on platinum chemo.