AstraZeneca and Daiichi’s drug Enhertu raises hopes for early breast cancer cure

AstraZeneca Plc and Daiichi Sankyo Co.’s cancer drug Enhertu bolstered outcomes for patients with early-stage breast cancer, results that could extend the blockbuster’s reach to tens of thousands more people and move it closer to a potential cure.

In two pivotal trials presented over the weekend at the European Society for Medical Oncology meeting in Berlin, Enhertu outperformed Roche Holding AG’s Kadcyla in preventing disease recurrence and showed promise when given before surgery. Daiichi shares rose as much as 3.1% in Tokyo trading Monday, helping the stock recover some of this year’s losses. It had fallen 8.2% year-to-date before the market opened amid concern over US tariff talks.

The findings mark a crucial test for Astra and Daiichi’s six-year alliance, which has already turned Enhertu into one of the world’s fastest-growing cancer medicines, generating $3.75 billion in sales last year. Discovered by Daiichi, the drug became the focus of Astra’s largest deal in more than a decade when it agreed to pay as much as $6.9 billion to co-develop it.

“The goal here is cure, so that’s what we’ve been driving towards,” said Ken Keller, Daiichi’s US chief executive officer, referring to the study of Enhertu before surgery. “What we’re hearing is that Enhertu is going to become the foundational treatment for early stage disease in HER2-positive disease.”

Enhertu is an antibody-drug conjugate — a treatment that delivers chemotherapy directly to tumor cells while limiting damage to healthy tissue. The studies focused on patients with HER2-positive breast cancer, which accounts for roughly one in five cases. Approval in early-stage disease could make the drug available to an estimated 130,000 additional patients across the Group of Eight industrialized nations, according to Astra.

In one study, more than 92% of patients who received Enhertu after surgery were alive and free of invasive disease three years later, compared with 84% among those treated with Kadcyla. The drug cut the risk of death or recurrence by 53%. Severe side effects were slightly more frequent on Kadcyla, though Enhertu caused more cases of interstitial lung disease, a potentially serious inflammation and scarring of lung tissue.

A separate study tested the drug before surgery. About two-thirds of patients given Enhertu had no remaining cancer in their breast or lymph nodes at the time of surgery, compared with 56% in the standard-therapy group. Those on Enhertu also reported fewer severe side effects. Researchers said data on long-term recurrence-free survival aren’t yet mature but show an early favorable trend.

Timing Question

The big question for doctors at the congress was whether the results mean Enhertu should be given before or after surgery. For Sara A. Hurvitz, a medical oncologist at Fred Hutchinson Cancer Center who wasn’t involved in either study, she is leaning toward using it after surgery, after standard chemotherapy, noting that there isn’t yet data for how long people live without the cancer recurring in patients that receive it before surgery.

Paul-Henri Cottu, an oncologist at Paris’s Institut Curie, who also wasn’t involved in the research, said he “was not very convinced” by the data on the use of Enhertu before surgery, adding that he wasn’t sure it would be enough for approval. Meanwhile, the benefit of Enhertu after surgery was clear, he said.

Having the data from both trials is a “real strength,” said Dave Fredrickson, executive vice-president of Astra’s oncology business, in an interview. “When the debate is around what’s the best early setting to use Enhertu, that is a good topic for the community to be wrestling with,” he said.