Sesen Bio has signed a definitive merger agreement to combine its business with Carisma Therapeutics and create a clinical-stage biotechnology firm in an all-stock deal. 

Carisma develops chimeric antigen receptor macrophage (CAR-M) therapies and is said to be the only firm developing such therapies with proof of mechanism and safety findings shown in clinical trials. 

Its CAR-M platform offers the potential to modify the specific targets of immune cells, thereby facilitating several therapeutic applications in oncology and beyond. 

The first clinical use of the CAR-M cell therapy technology is CT-0508, which is currently being assessed by the company in a multicentre Phase I trial for advanced HER2+ solid tumours.

The merged business will focus on the advancement of Charisma’s cell therapy platform, which leverages engineered macrophages and monocytes to transform the way cancers and other serious ailments are treated. 

The combined business is anticipated to have nearly $180m in cash, cash equivalents and marketable securities at the transaction’s closing, including $30m from a concurrent financing by Carisma. 

The companies aim to use these cash proceeds to progress Carisma’s pipeline through several ongoing and anticipated key data readouts across various clinical trials. 

They will also be used for funding operating expenses and capital expenditure needs up to 2024. 

On closing of the deal, the merged company will be called Carisma Therapeutics, and its headquarters will be located in Philadelphia, Pennsylvania, US.

Carisma president and CEO Steven Kelly will lead the combined business.

The boards of directors of Sesen Bio and Carisma have granted unanimous approval for the deal.

Subject to the necessary approvals and closing conditions, the business combination is anticipated to conclude in the coming three to four months.

Kelly said: “This transaction will provide us with financial strength to not only continue to develop our lead candidate, CT-0508, but also allow us to accelerate the growth of our platform and pipeline within and outside of oncology and develop additional strong strategic partnerships beyond those we already have with Moderna and Novartis.”

Last August, the US Food and Drug Administration declined to grant approval for Sesen Bio’s biologics license application for Vicineum to treat BCG-unresponsive non-muscle invasive bladder cancer.

Cell & Gene Therapy coverage on Pharmaceutical Technology is supported by Cytiva.

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