Immunome, Morphimmune reverse merge, with ex-Seagen CEO Clay Siegall to lead a year after domestic abuse arrest

Immunome and Morphimmune will come together as one company through a reverse merger, placing Clay Siegall, Ph.D.—who left his role as CEO of Seagen last year after being arrested for domestic abuse—in the chief executive chair.

The deal will see Immunome absorb Morphimmune through a reverse subsidiary merger, with the former’s shareholders owning 55% of the stock, according to a Thursday press release. The combined company will assume the Immunome name and ticker symbol and be headquartered in Seattle. Lab research facilities will also remain in Exton, Pennsylvania, and West Lafayette, Indiana. Both companies’ boards have approved the merger, which is expected to close by the end of the year. Financial details of the deal were not disclosed.

Clay Siegall Seagan
Former Seagen CEO Clay Siegall, now CEO of Immunome
  (Dimitrios Kambouris/Getty Images for Gabrielle's Angel Foundation)

At the same time, the companies are raising $125 million in a private placement deal. Participants include Enavate Sciences, EcoR1 Capital, Redmile Group, Janus Henderson Investors, Avidity Partners, Woodline Partners LP and others. Enavate CEO James Boylan will take a seat on Immunome’s board.

The company will then move forward in advancing the Immunome-discovered anti-IL-38 mAb, a folate receptor-targeted TLR7 agonist (FA-TLR7a) and FAP-targeted radioligand. Three investigational new drug applications are expected to be filed within 18 months after closure of the deal. A submission for the anti-IL-38 program is expected in the first quarter of 2024.

Immunome could also explore strategic in-licensing and further acquisitions, according to the release. The company will do so with Siegall at the helm, who brings a wealth of experience running Seagen including executing the acquisition of Cascadian Therapeutics in 2018.

While Siegall co-founded ADC cancer specialist company Seagen and turned it into a highly successful pharmaceutical company, his tenure ended in resignation in May 2022 after he was arrested for alleged domestic abuse. Siegall spent 33 hours in jail, but later prosecutors declined to charge him. He has denied the allegations. The merger press release did not mention his departure from the company, instead praising his previous work.

“Clay Siegall’s track record of drug development and shareholder value creation is exceptional, and we are honored to have him serve as chairman and CEO after the merger closes,” said Michael Rapp, Immunome board chairman. “By building on the accomplishments of Purnanand Sarma and the Immunome team, Clay will be positioned to develop best-in-class targeted cancer therapies across multiple modalities.”

Siegall took the helm at oncology-focused Morphimmune in March. Seagan has since entered a deal to be acquired by Pfizer for $43 billion, although the transaction has yet to close.

Morphimmune spun out of research from Philip Low, a distinguished professor of chemistry at Purdue University.