The US Food and Drug Administration (FDA) has granted approval to Citius Pharmaceuticals for its drug Lymphir (denileukin diftitox), a novel treatment for relapsed or refractory cutaneous T-cell lymphoma (CTCL). This approval comes after the drug was initially turned down by the FDA a year ago due to requests for additional product testing information. Lymphir represents a significant milestone for CTCL patients, a group with limited treatment options and no universally defined single treatment.
Lymphir is a recombinant fusion protein that combines an IL-2 binding domain with diphtheria toxin fragments, designed to target and kill leukaemic cells. It is a reformulated and purified version of Eisai's Ontak, which was first approved in 1999 but withdrawn in 2014 due to manufacturing issues. The rights to Lymphir were licensed to Citius by Dr Reddy's Laboratories, which had acquired them from Eisai in 2016.
CTCL is a rare and chronic cancer characterized by debilitating skin lesions and severe itching, affecting approximately 2,500-3,000 new patients in the US each year. The approval of Lymphir is expected to expand the CTCL treatment landscape, offering a new hope for patients with relapsed or refractory forms of the disease. Leonard Mazur, Citius' chief executive, highlighted the drug's potential to rapidly reduce skin disease and control symptomatic itching without cumulative toxicity.
A phase 3 trial completed at the end of 2021 demonstrated that Lymphir had an objective response rate of 36%, with almost 9% complete responses. In about half of the responding patients, the cancer was kept under control for at least six months. Citius is also exploring the use of Lymphir for peripheral T-cell lymphoma (PTCL) and immuno-oncology indications, which could offer larger sales potential if approved.
In addition to Lymphir, there is hope for CTCL patients with German Biotech's HDAC inhibitor Kinselby (resminostat), which has been filed in Europe based on data suggesting it can prevent relapse and postpone progression when used as a maintenance therapy.
