In $2.6B cancer deal, Seagen bets China's first homemade ADC can challenge Roche, AZ-Daiichi

U.S. antibody-drug conjugate leader Seagen is buying rights to an outside HER2 program from Chinese biotech RemeGen. (Seagen)

Antibody-drug conjugate leader Seagen is reaching for its wallet to scoop up rights to an outside program, and it’s set its eyes on the first antibody-drug conjugate (ADC) developed in China.

For $200 million upfront, Seagen is getting ex-Asia rights to Chinese biotech RemeGen’s HER2-targeted ADC disitamab vedotin. Up to $2.4 billion in potential biobucks is up for grabs if everything plays out across multiple indications. The deal also covers rights in Japan and Singapore. 

While Seagen already markets the HER2 small-molecule inhibitor Tukysa, the deal gives the U.S. cancer specialist an ADC that poses a direct threat to Roche’s Kadcyla and AstraZeneca and Daiichi Sankyo’s Enhertu in the HER2 cancer field, where the top players are reaping billions.

Pharma watchers expect Enhertu to reach $5.7 billion sales in 2030, and Kadcyla looks on track to reel in more than $2 billion sales this year.

The news comes just two months after disitimab vedotin won a conditional nod from China’s National Medical Products Administration to treat stomach cancer following at least two prior systemic therapies. The approval made the drug China’s first home-grown ADC to receive a go-ahead anywhere.

Disitimab vedotin won the nod thanks to data from a pivotal phase 2 trial showing it triggered a response in 24.4% of patients with HER2 over-expressing gastric cancer after two lines of prior chemotherapy treatment.

In the U.S., disitimab vedotin bears an FDA breakthrough therapy designation for treating second-line HER2-positive bladder cancer. A phase 2 trial is set to explore that use.

“This collaboration leverages Seagen’s world-class expertise and knowledge of ADC development, manufacturing and commercialization to maximize the potential of disitamab vedotin,” Seagen CEO Clay Siegall said in a statement Monday. The addition of such a late-stage asset with multiple development opportunities “aligns strategically” with the company’s expansion plans, he added.

Seagen is to some extent familiar with disitamab vedotin’s construct as it’s the original developer of the drug’s payload-linker technology. The same tech is used in Seagen’s Adcetris and Astellas-partnered Padcev.

RELATED: RemeGen grabs one of the world's largest ever biotech IPOs

But the RemeGen ADC’s antibody component, disitamab, is a novel medicine. The other two FDA-approved HER2 ADC drugs—Kadcyla and Enhertu—both use Roche’s trastuzumab, or Herceptin, as their antibody.

Disitamab vedotin has shown greater tumor-binding ability and an increased tumor uptake rate compared with trastuzumab in preclinical models, Seagen and RemeGen said.

Further, Seagen also touted “promising combination activity” of disitamab vedotin with a PD-1 inhibitor in bladder cancer. In a phase 1b/2 trial in China, the pairing of distamab vedotin and Junshi Biosciences and Coherus BioSciences’ PD-1 inhibitor toripalimab induced an overall response rate of 100% among 16 newly diagnosed metastatic bladder cancer patients with varying levels of HER2 expression, according to data unveiled at the ASCO 2021 meeting in June.

Daiichi has previously paired Enhertu with Bristol Myers Squibb’s PD-1 drug Opdivo in HER2-expressing breast or bladder cancer, but that cocktail showed very similar efficacy to monotherapy Enhertu.

RELATED: AstraZeneca, Daiichi Sankyo build Enhertu's blockbuster case with breast cancer win against Roche's Kadcyla

Winning Seagen’s favor for a deal this size isn’t a cakewalk. Besides Adcetris and Padcev, the company has multiple ADC programs in the working, including Genmab-partnered tisotumab vedotin, which expects an FDA decision for cervical cancer in October. Last year, Merck & Co. signed on to collaborate on ladiratuzumab vedotin for triple-negative breast cancer.

As for RemeGen, the Yantai, China-based company pulled off one of the world’s largest biotech IPO with a $515 million raise on Hong Kong exchange last November. In addition to disitamab vedotin, the firm is developing ADCs targeting mesothelin, c-MET and Claudin18.2 for various types of cancer.

The Seagen deal “highlights the global potential of disitamab vedotin in the ADC arena and is a major milestone for us as we begin the journey to transform from a domestic to a global biopharmaceutical company,” Jianmin Fang, Ph.D, RemeGen’s CEO and chief scientific officer, said in a statement.