Seattle Genetics on Thursday won U.S. approval for its second drug, eight years after joining the ranks of commercial biotech companies with its blood cancer medicine Adcetris.
Cleared to treat advanced bladder cancer, Padcev was developed in collaboration with the Japanese drugmaker Astellas. The two companies will jointly sell the drug in the U.S., splitting profits and costs equally.
For Seattle Genetics, the approval caps a year in which the Washington-based biotech's market value has more than doubled, to approximately $20 billion. Investors' enthusiasm is rooted in the company's expanding pipeline, which, in addition to Padcev, includes a breast cancer drug that Seattle Genetics plans to file for approval in the first three months of next year.
The biotech plans to put another eight drugs into clinical testing over the next two years, an ambitious plan that company CEO Clay Siegall describes as evidence of Seattle Genetics' evolution beyond Adcetris.
"By the end of 2021, we're going to be approaching 20 drugs in development," Siegall said in an interview ahead of Padcev's approval. "Not all drugs work, and cancer is a very hard disease, but we're building up our research, our ability to manufacture, our ability to do clinical trials, all our regulatory groups and our commercial."
Padcev is an antibody-drug conjugate, a type of therapy that Seattle Genetics specializes in developing. For ADCs, an antibody designed to target tumors is paired with a chemotherapy capable of killing cancer cells.
In the case of Padcev, the drug homes in on a protein called Nectin-4 that's frequently expressed on the surface of bladder cancer cells. A Phase 2 study showed Padcev shrank tumors in 44% of 125 patients with previously treated urothelial cancer that had progressed. For 15, no cancer could be detected following treatment.
Padcev does come with a long slate of side effects, particularly elevated blood sugar levels, peripheral neuropathy and the potential for eye disorders. A full course of treatment costs between $110,000 and $120,000 on average, Seattle Genetics said.
Approval is only conditional, meaning Seattle Genetics and Astellas will need to prove Padcev's benefit in a larger, randomized study that is currently ongoing. The companies have also started another trial pairing Padcev with Merck & Co.'s immunotherapy Keytruda.
Combinations will likely be an important part of bladder cancer treatment moving forward, putting Seattle Genetics and Astellas in a strong position now that Padcev is approved. Four other drugmakers besides Merck currently sell immunotherapies for the tumor type, but their effectiveness as monotherapies is modest.
Seattle Genetics has been preparing for Padcev's approval, which came about three months ahead of schedule. It will rely on a salesforce of about 100 representatives, a similar size to what the company uses for Adcetris in blood cancer.
But "the salesforce has to be different than the lymphoma salesforce because they call on completely different doctors," Siegall said.
The company is also building out a salesforce for tucatinib, a breast cancer drug that it acquired in a 2018 buyout of Cascadian Therapeutics. Results released in October showed the kinase inhibitor sharply cut the risk of death when added to Roche's Herceptin and chemotherapy.
If approved, tucatinib would mark another milestone for Seattle Genetics and expand its portfolio outside of antibody-drug conjugates.