Actelion is looking to acquire Ceptaris, a privately-held US company in a deal that could be worth $250 million.

The deal is dependent on the US Food and Drug Administration giving the green light to Valchlor, which could be the first approved topical formulation of mechlorethamine for the treatment of early-stage mycosis fungoides-type cutaneous T-cell lymphoma. Valchlor has a Prescription Drug User Fee Act (PDUFA) date of August 27.

Mycosis fungoides is the most common type of cutaneous T-cell lymphoma, a rare form of non-Hodgkin's lymphoma. Patients get lesions which initially appear to be a rash and may progress to form plaques and disfiguring tumours. Early stage cases may be confused with other skin conditions until a definitive diagnosis is made based upon skin biopsy and most cases of mycosis fungoides are diagnosed in patients over 50.

Actelion has already paid $25 million and will fork out another $225 million if all goes well at the FDA. Ceptaris' shareholders are also eligible to receive additional payments based on net sales of Valchlor.

Actelion chief executive Jean-Paul Clozel said that should the FDA approve Valchlor and the acquisition goes through, "we would be able to offer this meaningfully differentiated medicine to patients who today are dependent on formulations prepared locally by compounding pharmacies in a non-standardised environment". He added that "at the same time, we would leverage our existing knowhow and infrastructure in the fields of orphan and ultra-orphan indications when appropriately commercialising Valchlor to specialists in the field of dermatology and oncology".