Roche’s Phase II/III GATSBY trial, designed to support a new indication for Kadcyla® (ado-trastuzumab emtansine) in second-line treatment of HER2-positive advanced gastric cancer, did not meet its primary endpoint, the drug’s co-developer ImmunoGen disclosed today.

ImmunoGen made the disclosure in a 68-word regulatory filing with the U.S. Securities and Exchange Commission. The filing did not detail how the trial failed.

“Roche expects the detailed clinical findings from GATSBY to be reported at a future medical conference,” the filing stated.

According to the trial’s page on, last updated by Roche on October 1, the GATSBY trial was a multicenter, randomized study designed to evaluate the efficacy and safety of Kadcyla compared to standard taxane treatment in patients with HER2-positive advanced gastric cancer. 

No study results were posted, either on or on Roche’s clinical trials website.

The GATSBY trial’s primary endpoint was overall survival (OS) over a time frame of approximately 3 years.

The trial had numerous secondary endpoints including progression-free survival, objective response rate, duration of response, safety, response distribution of treatment-related symptoms, time to gastric cancer symptom progression, quality of life, and three measures of pharmacokinetics.

ImmunoGen’s filing was submitted nearly seven months after ImmunoGen and a fund manager signed a deal concerning the company’s royalties from Kadcyla, developed by Genentech (now a Roche subsidiary) using antibody-drug conjugate technology under a 2000 agreement.

Under that deal, announced March 30, fund manager TPG Special Situations Partners (TSSP) agreed to pay ImmunoGen an immediate $200 million. In return, TSSP won the right to receive 100% of the royalty revenue on Kadcyla® commercial sales that would otherwise be paid by Roche to ImmunoGen until TSSP has received a total of either $235 million or $260 million, depending on timing.

After that threshold was met, ImmunoGen is eligible to receive 85% of the Kadcyla royalty revenue, with TSSP collecting the remaining 15% of the Kadcyla royalty revenue, until the revenue stream ends.

The royalty deal was expected to yield net proceeds to ImmunoGen of approximately $194 million.

“This transaction has met our objectives of obtaining significant cash while avoiding the dilutive effect of a stock offering and retaining for our shareholders the majority of upside from substantial Kadcyla sales development,” David B. Johnston, ImmunoGen EVP and CEO, said in a statement at the time.

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