Seattle Genetics wins another speedy approval as FDA clears breast cancer drug

In Clinical Studies News by Barbara Jacoby

By: Ben Fidler


Dive Brief:

  • The Food and Drug Administration on Friday ​approved Seattle Genetics’ drug Tukysa as a treatment for patients whose advanced breast cancer expresses the HER2 protein and has spread to other areas of the body, including the brain.
  • Approval comes four months ahead of the Aug. 20 deadline set by the FDA, a speedy review that follows other quick decisions for several recently cleared drugs. It’s just the second new drug approval granted under the agency’s “real-time oncology review,” a program designed to hasten decisions on cancer medicines.
  • The decision gives Seattle Genetics — best known for its blood cancer medicine Adcetris — a third marketed drug, and further validates the biotech’s 2018 buyout of Tukysa’s original developer, Cascadian Therapeutics.

Dive Insight:

Nearly 15 years passed from Seattle Genetics’ 1997 founding to approval of its first drug, Adcetris. Now, in the span of four months, the biotech’s added two more.

First came the bladder cancer drug Padcev, which the FDA approved on an accelerated basis in December and Seattle Genetics co-developed with Japanese drugmaker Astellas.

Like Seattle Genetics’ flagship drug Adcetris, Padcev is what’s known as an antibody-drug conjugate, or ADC, which combines the targeting power of an antibody with a tumor-killing toxin. The treatment is approved for patients who have failed a few treatments, but Seattle Genetics has a chance to move it into the frontline setting if an ongoing study combining the drug with the Merck immunotherapy Keytruda succeeds.

Approval of Tukysa marks another milestone for Seattle Genetics, which has seen its shares soar to record highs over the past year. Tukysa is an oral kinase inhibitor — a common type of cancer drug — rather than the ADCs for which the company is known.

Seattle Genetics owns full rights to Tukysa, too, thanks to a $614 million buyout of Cascadian Therapeutics in 2018. Approval expands the company’s reach into breast cancer, which affects more women than any other cancer type. The drug costs $18,500 per month at list price, or $111,000 per patient, per year, a company spokesperson confirmed to BioPharma Dive.

As with Padcev, which was approved three months before the FDA’s review deadline, Seattle Genetic’s Tukysa was cleared well ahead of schedule.

The biotech filed its application in December. The FDA began its review in February, and approved Tukysa two months later. That timeline is in line with some of the fastest drug approvals in recent memory, among them Novartis’ breast cancer drug Piqray, the only other new medicine cleared under the FDA’s “real-time oncology review” pathway. AstraZeneca and Daiichi Sankyo’s breast cancer drug Enhertu also received a fast review.

Tukysa’s currently under review in other countries as well under “Project Orbis,” a collaborative effort between the FDA and several other international regulators to simultaneously evaluate cancer drugs.

The fast approval came despite the ongoing coronavirus pandemic, which has stretched the healthcare system and drug regulators thin. The agency has hinted drug reviews might slow if other issues, such as maintaining drug supply, become more significant.

But Tukysa’s approval shows, at least for now, “how our regular work in reviewing treatments for patients with cancer is moving forward without delay,” said Richard Pazdur, the FDA’s top cancer drug evaluator, in a statement.

The approval is based on the results from the HER2CLIMB study, in which a regimen of Tukysa, Herceptin and chemotherapy cut the risk of death or disease progression significantly over Herceptin and chemo alone in patients with HER2-positive breast cancer. Those patients had already failed Herceptin and other HER2-targeting drugs, Perjeta and Kadcyla. The most common side effects seen were liver enzyme elevations and diarrhea.

Seattle Genetics also found Tukysa appeared to help patients whose cancers had spread to the brain — which occurs in about a quarter of HER2-positive breast cancer patients — and that’s reflected in the drug’s broader-than-anticipated label. The approval “unexpectedly enables” second-line use, whereas patients in the HER2CLIMB study had failed at least two therapies, wrote RBC Capital Markets analyst Kennen MacKay.

Seattle Genetics is testing Tukysa in a Phase 2 study in colorectal cancer that could lead to another fast approval, if successful.

Tukysa was the product of Cascadian, another Seattle-area biotech. Once known as Oncothyreon, Cascadian had a number of clinical setbacks over the years, among them a cancer vaccine known as Stimuvax. But a 2014 licensing deal with Array Biopharma — now owned by Pfizer — gave it tucatinib, which led Seattle Genetics to buy the company four years later.