Seagen, Astellas claim positive results in study key to cancer drug’s success

Dive Brief:

• Seagen and Astellas Pharma on Tuesday reported results from an important mid-stage study testing their bladder cancer drug Padcev together with Merck & Co.’s immunotherapy Keytruda in certain previously untreated patients.
• The development partners said they plan to discuss the data, which they described as positive, with health regulators. Treatment with the drugs shrank tumors in nearly 65% of treated patients in the study, according to the summary results released by the companies via press release. They plan to share additional data at an “upcoming scientific congress.”
• The data come from a cohort of a multi-stage study that randomized about 150 patients with advanced bladder cancer to receive either Padcev, or Padcev together with Keytruda. Participants had not previously received treatment for their disease and were ineligible for a type of chemotherapy called cisplatin.

Dive Insight:

Seagen and Astellas’ trial results are notable for several reasons. While their drug, Padcev, is already approved in the U.S. for advanced bladder cancer in patients who received other treatments, the companies aim to secure a broader market by proving it works well in previously untreated patients as well.

The mid-stage study data reported Tuesday could potentially allow Seagen and Astellas to seek an accelerated approval, although it’s not clear whether the Food and Drug Administration would agree. Analysts view a clearance in first-line bladder cancer as likely to propel significant sales.

The study readout is also one of two events that reportedly are drawing out talks between Seagen and Merck over a potential buyout of the biotechnology company. The Wall Street Journal reported in July that agreement on a deal was delayed to wait for the Padcev data as well as a decision in an arbitration case on potential drug royalties owed to Seagen.

“We think the stock will be up as some investors viewed these results as gating for the alleged [Merck] deal,” wrote Andrew Berens, an analyst at SVB Securities, in a July 26 note to clients. “We see the expected arbitration decision … as more unpredictable and a larger bottleneck for deal advancement,” he added.

Shares in Seagen rose by nearly 1.5% in Tuesday morning trading.

Overall, Seagen and Astellas disclosed few other details from the trial, such as the response rate data for patients who received only Padcev. Comparing monotherapy results to those for the Padcev-Keytruda combination will be important to determining the additional benefit the immunotherapy provides.

Still, the 65% response rate among those given the combination regimen comes in around analyst expectations for efficacy. Median duration of response — a measure of how long treatment can hold tumors in check — was not yet reached, meaning most patients were still in response at the time data was collected.

Significant adverse reactions were reported including rash, anemia, fatigue, low phosphate levels, sepsis and changes in liver enzyme levels, the companies said. Analysts noted they were looking for more information on skin reactions, which feature in a warning on Padcev’s labeling.

Seagen and Astellas are running three Phase 3 trials of Padcev together with Keytruda, including one designed to confirm the Phase 2 findings released Tuesday.

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