Pralatrexate Is An Effective Treatment for Heavily Pretreated Patients with Relapsed/Refractory Transformed Mycosis Fungoides (tMF)

Cutaneous T-cell lymphoma, which includes mycosis fungoides (MF) and the Sézary Syndrome, is an indolent T-cell lymphoma. Large-cell transformation (tMF) is a well-defined histopathological disease that is distinguished from primarily cutaneous MF by the presence of large cells that exceed 25% of total lymphoid infiltrate (Barberio et al. Br J Dermatol 2007; 157:284-9) and occurs in 11% to 23% of cases. tMF represents a significantly poorer prognostic subset of MF patients with median overall survival of 12 to 22 months from the time of diagnosis of large-cell transformation (Arulogun et al. Blood 2008; 112:3082-7). There is no standard therapy for tMF and most patients are treated with multiagent systemic chemotherapy regimens. Because of its poor outcome similar to that of aggressive peripheral T-cell lymphomas (PTCLs), tMF patients were included in PROPEL, the pivotal study that led to the accelerated approval of pralatrexate (FOLOTYN^®) in the United States for the treatment of relapsed or refractory PTCL.

Of 109 evaluable patients in the PROPEL trial, 12 patients had histologically confirmed tMF. All patients received pralatrexate at a dose of 30 mg/m² weekly for 6 weeks in a 7 week cycle.

Of the 12 patients with tMF, the median age was 56.5 years. The median number of prior therapies was 6.5 (range 1 to 12), and 5 patients (42%) received ≥5 prior systemic regimens. The majority of patients had received prior multiagent chemotherapy, including cyclophosphamide/doxorubicin/vincristine/prednisone (CHOP) or CHOP-based therapy in 67% of patients and other multiagent regimens in 17% of patients. Only 1 of 12 patients had a response to their most recent prior chemotherapy regimen. The objective response rate (ORR) to pralatrexate in this group of refractory tMF using International Workshop Criteria based on investigator assessment, was 58%. Consistent with the overall study population, the ORR by independent central review was 25%. The difference in ORR between independent central review and investigator assessment for tMF is mainly due to challenges with photodocumentation of response assessment of cutaneous lesions. The 12 patients with tMF received a median of 10 doses of pralatrexate and remained on treatment for a median of 89 days. The median response duration was 4.4 months and median PFS was 5.3 months, per investigator assessment. The median survival in this group of patients was 13 months. Mucosal inflammation was reported in 7 patients (58%) including 1 patient with grade 3. Grade 4 adverse events (AEs) were fatigue (1 patient) and thrombocytopenia (1 patient). Overall, patients with tMF were able to tolerate full-dose pralatrexate treatment, with no patients discontinuing due to an AE.

Pralatrexate demonstrated significant activity in the 12 refractory tMF patients enrolled in the PROPEL trial with an investigator assessed response rate of 58%. Pralatrexate should be considered as a treatment option for patients with tMF.

Foss:Allos Therapeutics, Inc.: Consultancy, Speaker. Horwitz:Allos Therapeutics, Inc.: Consultancy, Research Funding. Pinter-Brown:Allos Therapeutics, Inc.: Consultancy. Goy:Allos Therapeutics, Inc.: Consultancy, Honoraria. Pro:Allos Therapeutics, Inc.: Research Funding. Savage:Allos Therapeutics, Inc.: Consultancy, Honoraria. Shustov:Allos Therapeutics, Inc.: Honoraria, Research Funding. Zain:Allos Therapeutics, Inc. : Speakers Bureau. Koutsoukos:Allos Therapeutics, Inc.: Employment. Fruchtman:Allos Therapeutics, Inc.: Employment. O'Connor:Allos Therapeutics, Inc.: Research Funding.