AstraZeneca keeps the ball rolling on Daiichi-partnered Enhertu, picking up 2nd indication in gastric cancer
AstraZeneca’s big gamble on Daiichi Sankyo’s antibody-drug conjugate Enhertu has already paid off with a big approval in breast cancer more than a year ago. But the partners have big plans for their blockbuster in the making, and a new nod in gastric cancer will raise their spirits even higher.
The FDA on Friday approved Enhertu to treat locally advanced or metastatic HER2-positive gastric or gastroesophageal junction adenocarcinoma in patients who have previously undergone at least one round of treatment with a Herceptin-based regimen, AstraZeneca said in a release.
Enhertu, initially approved in late 2019 as a treatment for HER2-positive breast cancer, will now battle advanced gastric cancer, a hard-to-treat disease that comes with a poor prognosis. Roughly one in five late-stage gastric cancer patients are diagnosed with tumors that express the HER2 gene, AstraZeneca said in a release.
The FDA based its review on data from the pivotal Phase II DESTINY-gastric01 trial, with data showing Enhertu significantly extended patients’ lives over standard-of-care chemo. The trial patients had been treated with two prior rounds of a Herceptin-chemo combo.
Patients on Enhertu saw a 41% relative reduction in risk of death compared with patients treated with chemotherapy with a median OS of 12.5 months versus 8.4 months in the chemo arm, AstraZeneca said. Patients also posted an overall response rate of 40.5% on Enhertu versus 11.3% on chemo. In terms of complete and partial response, Enhertu posted rates of 7.9% and 32.5%, respectively, compared with 0% and 11.3% for chemo.
On top of that, patients administered the ADC hit a median progression-free survival of 5.6 months compared with 3.5 months in the chemo arm, and a median duration of response of 11.3 months versus 3.9 months for chemo.
The FDA gave Enhertu its priority review tag back in October on the strength of that data, strengthening a second front in AstraZeneca and Daiichi’s quest to take the ADC into a range of HER2 expressing tumors.
Within the span of a week in May, Enhertu scored two breakthrough designations in both gastric cancer and non-small cell lung cancer. That growth could spell more than $2 billion in peak sales by consensus estimates, although Daiichi has previously floated an internal estimate of up to $4.5 billion in peak sales if Enhertu reaches its maximum audience.
As Enhertu continues to pick up steam, it’s adding more and more reinforcement to AstraZeneca’s decision to partner up on the ADC back in early 2019 for $1.35 billion in upfront cash and a total possible payout of $7 billion. With the most recent approval, AstraZeneca will owe Daiichi $115 million in milestone payments, the drugmaker said.