Mersana Therapeutics' decision earlier this year to go all-in on its antibody-drug conjugate Emi-Le appears to have paid off—at least based on the $285 million deal Day One Pharmaceuticals has signed for the company.
The agreement will see California-based Day One hand over $25 cash per share of Mersana—equivalent to an upfront equity value of around $129 million. Mersana’s shareholders will also be eligible for a contingent value right of $30.25 per share if Emi-Le eventually hits certain clinical development, regulatory and commercial milestones.
Taking those milestone payments into account brings the deal’s total potential value to $285 million, according to a Nov. 13 release.
Mersana's stock closed trading yesterday at $8.87 per share. In early trading Thursday, the biotech's share price more than tripled.
At the heart of the deal is Emi-Le—also known as emiltatug ledadotin or XMT-1660—a dolasynthen ADC that targets B7-H4.
Massachusetts-based Mersana shared initial phase 1 data on Emi-Le in January and has since been running an expansion portion of the study in people with triple-negative breast cancer. In May, the biotech decided the best use of its remaining cash was to focus on this breast cancer opportunity, reducing research activities and eliminating its internal pipeline development efforts.
Day One CEO Jeremy Bender, Ph.D., described Emi-Le as a “potential game-changing new medicine” which, “if approved, will broaden our opportunities for patient impact and for continued growth and value creation.”
“The addition of the Emi-Le program to our portfolio allows us to leverage the research and development expertise, and the commercial capabilities, that already exist within Day One to address underserved, rare and life-threatening cancers in patients of all ages,” Bender added.
Day One already has a drug on the market in the form of Ojemda, which was the first drug approved by the FDA for a common type of childhood brain tumors. Last year, the biopharma paid $55 million upfront for the ex-China rights to MabCare Therapeutics’ PTK7-targeting ADC.
Mersana’s CEO Marty Huber, M.D., said the acquisition “recognizes the work that Mersana has done to develop Emi-Le and that the combination of Mersana’s assets and Day One’s research, development and commercial capabilities has the potential to bring more medicines to patients waiting for new therapies.”
“While Mersana has been focused on Emi-Le’s potential to treat patients with triple-negative breast cancer previously treated with topoisomerase-1 inhibitor ADCs, this transaction provides the near-term opportunity to support the development of Emi-Le for patients with adenoid cystic carcinoma, a population with very high unmet need,” Huber added.
Emi-Le isn’t the only ADC in Mersana’s pipeline. Back in 2022, GSK paid $100 million upfront for an option on Mersana’s HER2-directed ADC XMT-2056. Mersana still needs to complete dose escalation with enrichment for breast cancer patients in a phase 1 single-agent trial to round off the data package to support GSK’s opt-in decision.
In the past, Mersana has also been tapped up by Johnson & Johnson and Merck KGaA for research collaborations.