PS1096 INTERIM UPDATE FROM A MULTI‐CENTER STUDY OF PRALATREXATE IN ASIAN PATIENTS WITH RELAPSED OR REFRACTORY(R/R) PERIPHERAL T‐CELL LYMPHOMA (PTCL)

Background: Peripheral T‐cell lymphomas (PTCL) are a group of rare, aggressive and diverse lymphoproliferative disorder. When patients are in the relapsed/refractory setting, the survival is mostly less than 6 months. Pralatrexate, a folate analogue metabolic inhibitor, was the first monotherapy approved to treat R/R PTCL patients. As the subtypes difference between western and eastern countries, we would like to investigate the efficacy/safety of pralatrexate in Taiwanese patients. Aims: This single‐arm, multi‐center study aims to demonstrate the efficacy/ safety of pralatrexate in R/R PTCL patients. The patients who undergo Hematopoietic Stem Cell Transplantation (HSCT) or not after pralatrexate will be also investigated individually. Methods: Eligibility criteria included age ≧ 20 with PTCL according to the NCCN diagnosis criteria, the Revised European American Lymphoma (REAL), and WHO disease classification with the following subtypes: Peripheral T‐cell lymphoma, NOS (PTCL‐NOS), Angioimmunoblastic T‐cell lymphoma (AITL), Extranodal NK/T‐cell lymphoma, nasal type (ENKL), Enteropathy‐type T‐cell lymphoma (EATL), Hepatosplenic T‐cell lymphoma (HSTCL), Subcutaneous panniculitis‐like T‐cell lymphoma (SPTCL) and Adult T‐cell lymphoma/leukemia (human T‐cell leukemia virus [HTLV] 1+) (ATLL). Patients were documented disease progression after prior treatment. Intravenous pralatrexate was administrated weekly for 6 weeks in 7‐week cycles up to 5 cycles with concurrent vitamin B12 and folic acid. Patients who complete at least 1 cycle of pralatrexate and have at least 1 post‐treatment tumor assessment are defined as evaluable patients. The primary end point is Objective Response Rate (ORR, CR + PR). Secondary end points include Progression‐Free Survival (PFS), Duration of response (DoR) and Overall Survival (OS). Results: Twenty‐two patients were evaluable for efficacy per protocol definition. The subtype distribution included PTCL‐NOS (n = 9, 40.9%), AITL (n = 5, 22.7%), ENKL (n = 5, 22.7%), EATL (n = 1, 4.5%), SPTCL (n = 1, 4.5%) and ATLL (n = 1, 4.5%). The ORR was 54.5% with CR 18.2% (n = 4) and PR 36.3% (n = 8). When divided into 2 groups based on if patients received HSCT after pralatrexate, the ORR in HSCT group (n = 5) was 60% with CR 20% (n = 1) and PR 40% (n = 2), while ORR in non‐HSCT group (n = 17) was 53% with CR 18% (n = 3) and PR 35% (n = 6). At the time of data cut‐off, median PFS was 5 months (95% C.I. 5.51, 12.93), median DOR was 5.4 months (95% C.I. 2.64, 13.10) and OS not reached yet. It's notably that, among 5 patients that received HSCT successfully after pralatrexate, 4 patients are ENKL and the other is PTCL‐NOS. Except one who experienced disease progression after HSCT, the others still remain in response. It indicated that pralatrexate may play a beneficial role in bridging to transplantation in PTCL patients, especially in ENKL. Safety population analysis (n = 27) showed the most common TEAEs (grades 3–4) were: anemia (33%), stomatitis (26%), peripheral edema (22%), thrombocytopenia (15%) and leukopenia (11%). Summary/Conclusion: This interim update of this multi‐center study demonstrated the efficacy of pralatrexate monotherapy in R/R PTCL is 54.5%. Interestingly, most ENKL patients received HSCT after obtaining good disease control with pralatrexate. In addition, it showed tolerable safety profile. This is the first data demonstrated benefits of pralatrexate in R/R PTCL patients with intention or no intention to receive transplantation.