Seattle Genetics breaks into breast cancer with new approval Tukysa

Seattle Genetics is officially ready to make its first foray into the breast cancer field, thanks to some "stunning" data and a brand-new FDA approval that came four months ahead of schedule.

The agency Friday approved Tukysa (tucatinib) in combination with Roche’s Herceptin and chemo drug capecitabine for patients with metastatic, HER2-positive breast cancer who have received one or more prior anti-HER2 based regimens. That's "a much broader indication than the studied population," which was patients who have tried two prior therapies, Leerink Partners analyst Andrew Berens wrote in a note to clients.

"Given the current treatment paradigms, we believe this label opens the door for clinicians to use the drug in the second-line setting, as well as eventually in the first-line, in patients who have received a HER2 agent in the adjuvant/neoadjuvant setting," he wrote.

And in second-line patients, "the company believes it can compete" with Roche's Kadcyla, especially in patients with brain metastases, J.P. Morgan analyst Cory Kasimov wrote in his own investor note.

The drug’s list price will run at $18,500 for a 30-day supply, bringing the average cost of a course of treatment to $111,000 per patient.

“We think that the price we have come up with is in line with other recently approved novel cancer meds in similar-sized patient populations,” CEO Clay Siegall said, adding that, “we feel our data is extraordinary and provides substantial value to the patients.”

The company will also field support services, including copay assistance and free medicine for uninsured and underinsured patients.

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The FDA based its approval on results showing the Tukysa regimen could slash patients’ risk of death by 34% and significantly delay disease progression among patients whether or not they had brain metastases. Roughly half of patients in SeaGen’s Her2Climb trial had tough-to-treat brain metastases, Siegall said, noting that it was “a very high bar to hit, and our data was stunning.”

Berens and Leerink colleagues expect to see Tukysa pull in peak revenues of about $1.6 billion in metastatic breast cancer, with about $700 million of that haul "driven by usage in patients with brain mets across different lines of therapy," he said.

Now, the company’s job will be to get the word on Tukysa out to doctors, a task the ongoing COVID-19 pandemic certainly won’t make any easier. Still, the company has prepped its field force—consisting of a little more than 100 people, between the sales and medical affairs teams—for a virtual rollout, and SeaGen will be providing the drug to patients “certainly within a week” of approval.

“There will be virtual meetings” and “digital information that connects them to our label,” Siegall said, with the field force serving as “a source of information to make sure that doctors and their patients get what they need to make the right decisions.”

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Breast cancer is new territory for SeaGen, whose other two approved drugs—Adcetris and the newly approved Padcev—fall into the blood cancer and bladder cancer categories, respectively. But it’s nothing new for the crop of sales reps who will be taking Tukysa out into the field.

“We have built an amazing group of commercial folks … They’re trained, they’re very experienced in the world of breast cancer and cancer, but most of them have breast cancer experience,” Siegall said.

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In the meantime, SeaGen isn’t planning to stop with its breast cancer OK. It’s also studying Tukysa in colorectal cancer, where the drug has already produced a 52% response rate in a Herceptin combination study.

“We really are building on that and looking forward to the potential for our next label,” Siegall said.