Merck KGaA has signed a licensing deal for Opexa Therapeutics' investigational T-cell therapy for multiple sclerosis.

Tcelna (imilecleucel-T) is a potential first-in-class personalised treatment which is currently in mid-stage trials for patients with secondary progressive MS. It has also received fast-track designation from the US Food and Drug Administration.

The treatment is manufactured using ImmPath, Opexa's proprietary method for the production of a patient-specific T-cell immunotherapy, which involves the collection of blood from the MS patient. The companies note that expanded, irradiated T-cells are reintroduced into the patient via subcutaneous injection to trigger a therapeutic immune system response.

Cashwise, Opexa will receive an upfront payment of $5 million for granting an option to Merck for the Tcelna MS programme which may be exercised "prior to or upon completion of" an ongoing Phase IIb study. If the German group likes what it sees, it will pay another $25 million (or $15 million, (depending upon whether certain conditions are met), and in return receive worldwide development and commercial rights to Tcelna (imilecleucel-T) in MS, excluding Japan.

The Darmstadt-based group's Merck Serono unit will then be responsible for funding clinical development, although Opexa has a co-funding option. The US firm could bank a further $195 million, plus tiered royalties.

Susan Herbert, head of global business development and strategy at the Merck Serono division, said the agreement illustrates the company's commitment "to employ creative ways of accessing external innovation to develop potential next generation MS treatments, especially in SPMS, an area of high unmet need". Opexa chief executive Neil Warma said that "we could not ask for a more experienced partner to carry Tcelna", adding that his firm is pleased to retain important rights, including those for all indications outside MS.

Opexa's shareholders are certainly pleased with the deal and the company's stock soared 160% to $3.15 per share.