Horton, Bethany J.

Abstract Background: Patients with relapsed or refractory (R/R) peripheral T-cell lymphoma (PTCL) have a poor prognosis with median overall survival of ~3-12 months with current therapies, highlighting an urgent unmet need for novel therapeutics. PTCL is uniquely sensitive to epigenetic modifiers. We have shown that DNMT3 inhibitors like 5-azacytidine have potent immunomodulatory effects, including upregulation of cancer testis antigens, in pre-clinical models of T-cell lymphoma. Similarly, we have shown that pralatrexate (PTX) is potentially synergistic with drugs targeting epigenetic regulation. These data suggest a role for combining the immune checkpoint inhibitor pembrolizumab (pembro) with epigenetic agents in patients with PTCL. Methods: PTCL-002 is a multicenter, multi-arm phase Ib study designed to evaluate the safety and efficacy of pembro in combination with PTX and/or decitabine (DAC) in patients with R/R PTCL and CTCL. The study included three arms: arm A (pembro+PTX), arm B (pembro+PTX+DAC), and arm C (pembro+DAC). All patients received pembro 200 mg by IV infusion every 21 days. Dose selection for DAC and PTX in arms A and C, respectively, was based on a continual reassessment method (CRM) while arm B used a partial order CRM. Primary endpoints included MTD, RP2D, dose-limiting toxicities (DLT) and clinical efficacy as assessed by overall response rate (ORR). Secondary endpoints included progression-free survival, duration of response, and overall survival. Select pharmacokinetic and pharmacodynamic endpoints were also included in order to assess immune modulation and identify potential predictors of response. Results: We enrolled 26 patients, including 9 patients in arm A, 7 in arm B, and 10 in arm C. Median age was 61 (range 27-77) with 13 males and 13 females. Racial demographics were as follows: White 62%, Black 23%, Asian 3%, and Hispanic 1%. Median number of prior treatments was 3 (range 1-6). Histologic subtypes included ATLL (n=1), AITL (n=4), PTCL-NOS (n=10), SS (n=1), MF (n=6), PCALCL (n=1), MEITL (n=1), PCAECTL (n=1), and TFh-PTCL (n=1). Twenty-four of 26 patients received at least one dose of study drug and were evaluable for toxicity. Twenty-one of 26 of patients received at least one full cycle of therapy and were evaluable for response. Reasons for early discontinuation included consent withdrawal (n=1), rapid disease progression during cycle 1 (n=2), adverse event (n=1), and investigator decision (n=1). One DLT was observed each in arms A and B for prolonged grade 3 thrombocytopenia and febrile neutropenia, respectively. Three DLTs were observed in arm C including one patient with grade 3 hyponatremia and rash; one patient with grade 4 thrombocytopenia, neutropenia, and anemia; and one patient with grade 4 neutropenia. There were no treatment related deaths. Based on the observed DLTs, the RP2D for DAC in combination with pembro is 20 mg/m2on days 1-3; the RP2D for PTX in combination with pembro is 30 mg/m2on days 1, 8, and 15; for the triplet combination, the RP2D for DAC is 10 mg/m2given on days 1-5 and the RP2D for PTX is 20 mg/m2given on days 1, 8, and 15. Among 21 evaluable patients, responses were as follows: ORR 19% (4/21), CR 10% (2/21), PR 10% (2/21), and disease control rate (defined as proportion of patients with stable disease or better) 38% (8/21). ORR among evaluable patients in arms A, B, and C were 40% (2/5), 29% (2/7), and 0% (0/9), respectively. Analysis of serum cytokine levels in select patients (4 in Arm A, 4 in Arm B, and 5 in Arm C) revealed significant changes in 5 cytokines when compared to healthy age- and sex-matched controls. Of the 5 cytokines, 3 pro-inflammatory cytokines, TNFα, MIP-3α and IL-10, measured at day 1 pre-treatment were significantly higher in trial patients (p= 0.0001, 0.0008 and 0.003 respectively) than in healthy controls. Trial patients who responded to treatment (PR/CR) in any arms demonstrated a decline in serum levels of TNFα and IL-10 by day 15 of cycle 1, whereas non-responders (PD/SD) showed stable to increased levels of both TNFα and IL-10. Conclusion: We successfully identified the RP2D for DAC and/or PTX in combination with pembro in patients with R/R PTCL and CTCL. We demonstrated that an epigenetic platform incorporating the immune checkpoint inhibitor pembrolizumab is safe in heavily pretreated disease. More work on changes in cytokine profiles is needed before drawing any conclusions on their relationship to response.

This pathology PILOT study aims to define the role and feasibility of centralized pathology review in a cohort of 75 patients from different centers in the United States and Europe using digital slide scanning. The pathologic material from 75 patients who had been diagnosed with mycosis fungoides/Sézary syndrome and were clinically staged as IIb or above was retrieved from 11 participating centers. Each pathology reviewer was provided with the pathologic diagnosis (by the referring pathologist), and the following list of histopathologic criteria (presence or absence) from the initial report: epidermotropism, folliculotropism (FT), large cell transformation, syringotropism, and granulomas. Patients with advance stage were selected for this study as this is a population where there is significant variability in the diagnosis of pathologic prognostic and predictive biomarkers. The slides were digitally scanned with an Aperio scanner and consensus review of cases occurred when major or minor discrepancies between the referral diagnosis and central pathology review occurred. Among the 75 cases, 70 (93.3%) had a final consensus diagnosis between the 3 central review pathologists. The overall agreement between the consensus review and the referring pathologist was 60%. The overall agreement was also higher between the reviewers and consensus review, compared with the referring pathologist and consensus. 65.3% of cases had some type of discrepancy (major or minor) between the outside and consensus review. Major discrepancies were seen in 34 of 73 cases (46.6%; 73 cases indicated a yes or no response). Minor discrepancies were seen in 32 of 75 (42.7%) of cases. Most of the major discrepancies were accounted by a difference in interpretation in the presence or absence of large cell transformation or FT. Most minor discrepancies were explained by a different interpretation in the expression of CD30. We found digital slide scanning to be a beneficial, reliable, and practical for a methodical approach to perform central pathology review in the context of a large clinical prospective study.