Campbell, Mary S.

Abstract Introduction Brentuximab vedotin (BV) is an ADC directed against CD30, a receptor expressed by malignant Reed-Sternberg (RS) cells present in the inflammatory/immune cell microenvironment of classical Hodgkin lymphomas (cHL). Through induction of immunogenic cell death, BV may prime an antitumor immune response via microtubule disruption of CD30-expressing RS cells (Gardai 2015). Tumor cells expressing PD-1 ligands use the PD-1 pathway to evade an immune response. Nivolumab (Nivo) blocks the PD-1 receptor, inhibits binding of PD-1 ligands, and restores an effective antitumor immune response. Targeted killing of CD30-expressing RS cells, concurrent with restoration of the immune response, may lead to higher complete response (CR) rates in patients (pts) with relapsed or refractory cHL (R/R HL), as well as improved durability of responses post autologous stem cell transplant (ASCT). Here we present updated results from the phase 1/2 study of BV + Nivo in pts with R/R HL. Methods BV + Nivo was evaluated in cHL that had relapsed or was refractory to frontline (FL) chemotherapy in adult pts (NCT02572167). Pts were excluded if they had received prior salvage therapy, BV or immuno-oncology therapy, or allogeneic SCT or ASCT. Pts were treated in 21-day cycles for up to 4 cycles. In Parts 1 and 2 of the trial, BV (1.8 mg/kg) was given on Cycle 1 Day 1 and Nivo (3 mg/kg) on Cycle 1 Day 8. For Cycles 2-4, BV and Nivo were given on Day 1. After the Cycle 4 response assessment, pts were eligible to undergo ASCT. The investigators assessed response per the Lugano Classification (Cheson 2014). Results 62 pts with R/R HL were enrolled in Parts 1 and 2; 61 pts received BV + Nivo, of whom 58 completed treatment (tx). 4 pts discontinued the study due to pt decision (2), AE (1), and investigator decision (1). Median age was 36 years, 52% were female, and 90% had received FL ABVD. 45% of pts had primary refractory disease and 31% experienced relapse within 1 year of FL therapy. Infusion-related reactions (IRRs) occurred in 41% of pts. Tx emergent AEs occurred in 98% of pts prior to ASCT (33% G3, 5% G4). Excluding IRRs, potential immune-related AEs (IrAEs) occurred in 84% of pts (10% G3, 3% G4) with 5 pts (8%) treated with systemic steroids for G4 pneumonitis, G4 pneumonitis and colitis, G2 pneumonitis, G3 diarrhea and G2 colitis, and G3 AST elevation. Among the 60 efficacy-evaluable pts, the CR rate was 62%, (48% of CR pts had Deauville ≤ 2) with an objective response rate of 85%; 5 pts (8%) had stable disease and 4 pts (7%) progressed on tx. At the time of this analysis, 39 pts had initiated ASCT with a median 5.1x106 CD34+ cells/kg (range; 3-60) collected. Median times to neutrophil and platelet engraftment were 12 and 15 days, respectively. Pts were followed for a median of 3 months from ASCT (N=39, range; 0-12) and 5.7 months from first dose (N=61, range; 1-17). BV and Nivo effects on the immune system were evaluated by peripheral blood immunophenotyping, serum cytokine/chemokine analyses, T-cell receptor sequencing, and intracellular cytokine staining. The first dose of BV resulted in elevation of pro-inflammatory cytokines and chemokines and concurrent reduction in serum TARC levels, with these results maintained post Nivo. We observed a reduction in Tregs and other T cell subsets after the first dose of BV with an elevation of T cell subsets post BV + Nivo. While TCR clonality in the periphery did not change over the course of the trial, T cell clonal expansion was observed post BV + Nivo, concurrent with T cell elevation measured by flow cytometry. Ex vivo peptide stimulation of PBMCs isolated from blood revealed the enhanced ability of T cell subsets to respond to MHC I and MHC II antigens following BV + Nivo compared to baseline: e.g., effector memory CD8+ T cells from some pts displayed increased intracellular IL-2, and TNFa after stimulation with MHCI and MHCII peptide pools compared to baseline, potentially indicating elevated activation status of the immune system following combination tx. Conclusion R/R HL remains an unmet clinical need despite recent medical advances. These data suggest the combination BV + Nivo is a well tolerated and an active salvage therapy with a high rate of CR (62%) that has no adverse impact on stem cell collection. The safety and activity of this novel combination support further exploration in an ongoing pivotal phase 3 trial in pts with R/R HL who have either already received or are considered ineligible for ASCT (NCT03138499). Disclosures Herrera: Seattle Genetics: Research Funding; Merck: Consultancy; Genentech: Consultancy; BMS: Consultancy; Pharmacyclics: Consultancy. Moskowitz: Seattle Genetics: Honoraria, Research Funding; Takeda: Honoraria; Incyte: Research Funding; ADC Therapeutics: Research Funding; Bristol Myers-Squibb: Consultancy, Research Funding. Bartlett: Novartis: Research Funding; ImaginAB: Research Funding; Astra Zeneca: Research Funding; Millenium: Research Funding; Janssen: Research Funding; Pharmacyclics: Research Funding; Affimed: Research Funding; Forty Seven: Research Funding; Immune Design: Research Funding; Bristol-Meyers Squibb: Research Funding; Merck & Co: Research Funding; KITE: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genentech: Research Funding; Seattle Genetics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Research Funding. Vose: Merck: Research Funding; Kite: Research Funding; Janssen: Research Funding; Celgene: Research Funding; Allos Therapeutics: Research Funding; Acerta: Research Funding; Incyte: Research Funding; Onyx: Research Funding; Seattle Genetics: Research Funding; US Biotest: Research Funding; Bristol-Myers Squibb: Research Funding. Ramchandren: Seattle Genetics: Consultancy; MERCK: Research Funding; Pharmacyclics: Research Funding; Janssen: Research Funding. Feldman: AbbVie: Speakers Bureau; Janssen: Speakers Bureau; Kite Pharma: Speakers Bureau; Celgene: Speakers Bureau; Pharmacyclics: Speakers Bureau; Seattle Genetics: Honoraria, Research Funding, Speakers Bureau; Bristol-Myers Squibb: Consultancy. LaCasce: BMS: Consultancy; Forty Seven: Consultancy, Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Consultancy, Research Funding. Ansell: Merck: Research Funding; Bristol-Myers Squibb: Research Funding; Celldex: Research Funding; Seattle Genetics: Research Funding; Affimed: Research Funding. Moskowitz: Celgene: Consultancy; Seattle Genetics: Consultancy, Other: Ad Board, Research Funding; Genentech BioOncology: Consultancy; Pharmacyclics: Research Funding; Merck: Consultancy, Research Funding. Fenton: Seattle Genetics: Employment, Equity Ownership. Ogden: Seattle Genetics: Employment, Equity Ownership. Taft: Seattle Genetics: Employment, Research Funding. Zhang: Seattle Genetics: Employment, Research Funding. Kato: Bristol-Myers Squibb: Employment, Equity Ownership; Seattle Genetic: Research Funding. Campbell: Seattle Genetics: Employment, Equity Ownership; CTI BioPharma: Employment, Equity Ownership. Advani: Agensys: Research Funding; Pharmacyclics: Research Funding; Regeneron: Research Funding; FortySeven: Research Funding; Nanostring: Consultancy; Celgene: Research Funding; Pharmacyclics: Consultancy; Merck: Research Funding; Juno Therapeutics: Consultancy; Kura: Research Funding; Janssen: Research Funding; Millennium: Research Funding; Seattle Genetics: Research Funding; Gilead: Consultancy; Bristol-Myers Squibb: Consultancy, Research Funding; Spectrum: Consultancy; Bayer Healthcare Pharmaceuticals: Research Funding; Infinity: Research Funding; Genentech: Research Funding; Cell Medica: Research Funding; Sutro: Consultancy.

Abstract Background and Aims A platelet count ≤100,000/µL is regarded as an independent prognostic marker for the development of leukemia and is associated with inferior survival in myelofibrosis (MF) (Huang et al. 2008). The approved JAK2 inhibitor, ruxolitinib, is associated with treatment-emergent thrombocytopenia, and patients with platelets ≤100,000/µL were excluded from the phase III COMFORT trials. Efficacy and safety data are limited in patients with MF and platelets ≤100,000/µL treated with ruxolitinib. Pacritinib (SB1518), an oral JAK2/FLT3 inhibitor, did not appear to be associated with clinically significant treatment emergent anemia or thrombocytopenia during early phase studies in patients with myeloid and lymphoid malignancies. This integrated analysis was performed to further evaluate the safety and efficacy of pacritinib in MF patients with baseline platelet counts of ≤100,000/µL. Methods The databases from 2 phase I/II clinical trials of pacritinib in advanced myeloid malignancies and MF were integrated to evaluate the rate of adverse events (AEs) and favorable spleen responses in patients with MF and thrombocytopenia. Results One hundred twenty-nine patients with advanced myeloid malignancies and MF were treated with pacritinib in phase I and II clinical trials. Sixty-five patients with MF were treated with 400 mg orally once daily in 2 phase II studies. Of these, 28 patients with MF [21 primary MF (75%), 5 post-polycythemia vera-MF, 2 post-essential thrombocytosis-MF] had baseline platelet counts of ≤100,000/µL (median: 58,500/µL, range: 15,000/µL – 97,000/µL). The median age was 69 years. Twenty three (82%) patients had the JAK2V617F mutation. During the phase 2 studies, spleen volume responses were assessed by MRI and are shown for all patients (Figure 1) and for patients with platelets ≤100,000/µL (Figure 2). Thirty-seven percent and 43% of all evaluable patients and patients with ≤100,000/µL platelets, respectively, had ≥35% reduction in spleen volume from baseline (Table). Among the 21 informative patients with allelic JAK2V617F quantification at more than 1 study visit, 3, including 2 patients with homozygous mutations, had ≥35% reduction in spleen volume and substantial reductions in allelic burden from baseline (mean reduction 64%, range 44 to 88%). In the 11 (17%) patients with MF and baseline platelet counts ≤50,000/μL, overall spleen volume reduction was 38% (3/8) in evaluable patients and the median decline in platelet count observed at study end was 6,000/µL. Integrated safety analysis for all 129 patients with advanced myeloid malignancies showed the most common adverse events (AEs) were gastrointestinal (GI), predominantly diarrhea, and most of these were grade 1 (43%) and grade 2 (26%). The time to onset of diarrhea was ≤30 days in the majority of those affected, but only 2% had drug discontinuation as a consequence. Among the 129 patients in the phase 1 and 2 trials, 57 patients had ≤100,000 platelets; of these 26 (46%) had no CTC grade change in hemoglobin (Hb) and platelet counts from baseline values. Hb and platelet counts improved by one grade in 16% and 18% of patients, respectively. One grade worsening was seen in 28% and 30% in Hb and platelet counts, respectively. Conclusions Pacritinib was well-tolerated in patients with MF, regardless of their baseline platelet counts. Grade 1 or 2 GI toxicities, particularly diarrhea, were the most common AEs. Spleen responses were similar in patients regardless of baseline platelet counts (≥100,000/µL vs. ≤100,000/µL). Notably, even patients with initial platelet counts ≤50,000/µL tolerated therapy and the majority maintained stable hemoglobin and platelet counts. A phase III trial will evaluate pacritinib versus best available therapies in patients with MF and platelet counts ≤100,000/µL. Disclosures: Dean: Cell Therapeutics, Inc: Employment. Cernohous:Cell Therapeutics, Inc: Employment. Mesa:Incyte, CTI, Gilead, Celgene, Genetech, NS Pharma, Lilly: Research Funding. Campbell:Cell Therapeutics, Inc: Employment. Caldwell:Cell Therapeutics, Inc: Employment. Wang:Cell Therapeutics, Inc.: Employment. Myint:Cell Therapeutics, Inc: Employment.

TPS7577 Background: Nivolumab (nivo) is a PD-1 immune checkpoint inhibitor that augments T-cell activation and host anti-tumor responses. PD-1 blockade has shown promise in B- and T-cell non-Hodgkin lymphoma (NHL),1 but many patients (pts) with NHL do not respond or progress after response. Combination therapy using anti-tumor agents with complementary mechanisms of action and low immunosuppressive impact may result in more frequent and durable responses. Brentuximab vedotin (BV) is an anti-CD30 antibody–drug conjugate that induces cell cycle arrest and apoptosis, with activity in a range of NHL tumors.2,3 Tumor cells undergoing BV-induced apoptosis have shown subsequent immune-mediated anti-tumor cytotoxicity.4 Therefore, nivo and BV may synergize if combined for relapsed/refractory (RR) NHL. Methods: CheckMate 436 (NCT02581631) is a phase 1–2, open-label, international, single-arm study evaluating nivo + BV for CD30-expressing RR NHL (study start: Dec 2015) in pts with RR diffuse large B-cell lymphoma, peripheral T-cell lymphoma (excluding anaplastic large cell lymphoma), and cutaneous T-cell lymphoma (mycosis fungoides/Sézary syndrome); cohorts with primary mediastinal B-cell lymphoma (PMBL) and mediastinal gray zone lymphoma were made eligible in Sept 2016. Pts with PMBL must be aged ≥15 y (≥18 y for other histologies). All pts must have CD30-expressing disease, defined by CD30 on ≥1% of tumor cells or tumor-infiltrating lymphocytes by immunohistochemistry. In the phase 1 component, 6 pts will receive nivo and BV until disease progression or unacceptable toxicity. In the phase 2 component, ~130 more pts across the 5 histologies will be enrolled and treated at the recommended dose. Primary endpoints: safety, tolerability, and investigator-assessed objective response rate; secondary endpoints: duration of response and complete response (CR), CR rate, and progression-free and overall survival. Accrual is ongoing. References: 1. Lesokhin A et al. JCO 2016;34:2698–704 2. Jacobsen E et al. Blood 2015;125:1394–402 3. Horwitz S et al. Blood 2014;123:3095–100 4. Gardai S et al. Cancer Res 2015;75(15 Suppl):2469 [abstract]. Clinical trial information: NCT02581631.

Key Points BV and Nivo were well-tolerated in patients with R/R HL, with less than 10% of patients treated with systemic steroids for immune-related AEs. The complete response rate was 61% (82% objective response rate), and patients were able to undergo stem cell transplant without adverse impact.

Key Points Pacritinib reduced myelofibrosis-related splenomegaly and patient symptoms without causing clinically significant myelosuppression. Pacritinib had activity and was well tolerated in patients with preexisting anemia and thrombocytopenia.