Abstract: In patients with metastatic castration-resistant prostate cancer (mCRPC), resistance to androgen receptor (AR)-targeted therapies, such as enzalutamide, remains an issue. Inactivation of inhibitory PTEN activates PI3K/AKT signaling and contributes to resistance to androgen deprivation therapy and poor outcomes. Therefore, dual targeting of AR and PI3K/AKT pathways may limit tumor growth and reverse resistance. Patients and Methods: In this phase I study (NCT02215096), patients with PTEN-deficient mCRPC who progressed on prior enzalutamide received once-daily enzalutamide 160 mg plus PI3Kβ inhibitor GSK2636771 at 300 mg initial dose, with escalation or de-escalation in 100-mg increments, followed by dose expansion. Primary objectives were to evaluate safety/tolerability, determine the recommended phase II dose, and assess the 12-week non-progressive disease (PD) rate. Results: Overall, 37 patients were enrolled; 36 received ≥1 dose of GSK2636771 (200 mg: n = 22; 300 mg: n = 12; 400 mg: n = 2) plus 160 mg enzalutamide. Dose-limiting toxicities occurred in 5 patients (200 mg: n = 1; 300 mg: n = 2, 400 mg: n = 2). No new or unexpected adverse events or evidence of drug–drug interaction were observed. At the recommended dose of GSK2636771 (200 mg) plus enzalutamide, the 12-week non-PD rate was 50% (95% confidence interval: 28.2–71.8, n = 22); 1 (3%) patient achieved a radiographic partial response lasting 36 weeks. Four of 34 (12%) patients had prostate-specific antigen reduction of ≥50%. Conclusions: Although there was acceptable safety and tolerability with GSK2636771 plus enzalutamide in patients with PTEN-deficient mCRPC after failing enzalutamide, limited antitumor activity was observed.

Abstract: OFA was approved for the treatment of fludarabine and alemtuzumab refractory CLL on the basis of a single-arm study which also included pts with BFR CLL. This open label, randomized, Phase III study of OFA or PC treatment in pts with CLL refractory to fludarabine and with bulky lymphadenopathy (at least one lymph node 〉 5 cm) was conducted to confirm the results of OFA in BFR pts and also through a 2nd randomization to compare extended OFA (12 months) vs. approved regimen of OFA (6 months). PC was considered an appropriate comparator for these pts given the lack of a consensus around standard of care treatment for this difficult-to-treat population. Pts were randomized 2:1 to receive either the approved regimen of 8 weekly infusions of OFA followed by 4 monthly infusions (Dose 1, 300 mg; Doses 2–12, 2000 mg) or PC of non-OFA containing therapy, including treatments approved for CLL and well established standards of care for up to 6 months. Pts in the OFA arm who had an investigator-assessed CR, PR or SD underwent a 2nd 2:1 randomization to 6 additional OFA infusions 2000 mg every 4 weeks (OFA Ext), or observation (Obs). Pts in the PC arm who developed disease progression during the study could receive OFA salvage therapy for up to 12 months of treatment. Premedication for OFA infusions consisted of glucocorticoid, paracetamol, and antihistamine. The primary objective of this study was to evaluate progression-free survival (PFS) with OFA treatment versus PC as assessed by an Independent Review Committee (IRC). Response assessments were performed using the 2008 Update of the NCI-WG CLL Guidelines [Hallek, 2008] . Secondary endpoints included overall response rate (ORR), time to next therapy (TNT), overall survival (OS), and safety. 122 pts were randomized (79 OFA, 43 PC). Pts completed a median of 12 OFA infusions and 3 months PC therapy. The median PFS (mPFS) as measured by IRC was 5.4 months for OFA and 3.6 months for PC (hazard ratio [HR] 0.79, p=0.27, stratified log rank test; Fig 1). Median PFS as assessed by the investigator (INV) was 7.0 months for OFA and 4.5 months for PC (HR 0.56, p=0.003). The median time to start of next anti-CLL treatment was 11.5 months for OFA and 6.5 months for PC (p=0.0004, stratified log rank test). The ORR (95% CI) by IRC evaluation was 38% (27%, 50%) for OFA and 16% (7%, 31%) for PC (p=0.02). 37 pts underwent a 2nd randomization to either OFA Ext (n=24) or Obs (n=13). From 2nd randomization, mPFS (INV) was 5.6 months for OFA Ext and 3.5 months for Obs (HR: 0.49, p=0.026, stratified log rank test) (Fig 2). Grade ³3 infusion reactions occurred in 5% of pts in the OFA arm with no fatal reactions in either arm. Grade ≥3 cytopenias in the OFA arm included neutropenia (24%, no prolonged neutropenia and 1 patient with late onset neutropenia), thrombocytopenia (8%), anemia (8%). Of the 43 PC pts, 22 received OFA Salvage with an ORR of 50% and mPFS of 5.4 months. Table of Response and Time to event Endpoints OFA (N=79) PC (N=43) Characteristics Median (range) Age, years 61.5 (46 – 82) 63 (40 – 76) No. prior therapies 4 (2 – 16) 3 (2 – 11) No. of infusions 12 (1 – 18) 3 (1 – 6) IRC Investigator Efficacy endpoints OFA PC p-value OFA PC p-value Responders, % 38% 16% 0.019 49% 37% 0.415 mPFS, months 5.36 3.61 0.267 7 4.5 0.003 OFA PC TNT, months 11.5 6.5 p=0.0004 OS, months 19.2 14.5 p=0.13 Figure 1. Kaplan-Meier Estimates of PFS by IRC (OFA vs. PC) Figure 1. Kaplan-Meier Estimates of PFS by IRC (OFA vs. PC) Figure 2. Kaplan-Meier Estimates of PFS by INV (OFA Ext vs. Obs from 2nd randomization) Figure 2. Kaplan-Meier Estimates of PFS by INV (OFA Ext vs. Obs from 2nd randomization) Conclusions: Although the study did not meet its primary endpoint of demonstrating statistically significant superior PFS by IRC, the ORR, PFS by investigator, TNT, and OS favor OFA and were consistent with previously reported results in BFR pts. There was also a longer PFS in pts who underwent the 2nd randomization to receive OFA Ext vs. the approved OFA treatment regimen of 6 months treatment. Disclosures Österborg: GSK: Research Funding. Off Label Use: Discussion of extended ofatumumab dosing (12 months) in addition to the approved 6 month dosing of ofatumumab in refractory CLL. Zaritskey:Novartis: Consultancy, Honoraria. Kaplan:GSK: Honoraria. Steurer:GSK: Consultancy, Honoraria, Research Funding. Schuh:GSK: Honoraria; Roche: Honoraria; Gilead: Honoraria; Celgene: Honoraria; Napp: Honoraria. Montillo:GSK: Honoraria. Kulyaba:GSK: Honoraria. Gorczyca:GSK: Employment. Daly:GSK: Employment. Chai-Ni:GSK: Employment. Lisby:Genmab: Employment. Gupta:GSK: Employment.

Abstract: Background BCMA is a cell surface receptor in the TNF superfamily with expression restricted to B lineage cells at later stages of differentiation, which is required for the survival of long lived plasma cells. BCMA is also expressed on MM cells. GSK2857916 is a humanized IgG1 anti-BCMA antibody conjugated to the microtubule disrupting agent monomethyl auristatin-F via a stable, protease-resistant maleimidocaproyl linker. Upon binding to BCMA, GSK2857916 is rapidly internalized and active drug released in the cell. GSK2857916 also exhibits enhanced antibody-dependent cell-mediated cytotoxicity resulting from afucosylation of the Fc domain, and potentially induces immunogenic cell death. Here we report results from the Part 2 expansion of a Phase 1 study of GSK2857916 in heavily pretreated MM pts. Methods BMA117159 (NCT02064387) is a Phase I, first in human, open-label study investigating GSK2857916 in relapsed/refractory MM and other hematologic malignancies expressing BCMA. The primary objective is safety and determination of maximum tolerated dose and recommended Phase 2 dose (RP2D); secondary objectives include pharmacokinetics (PK), antidrug antibody (ADA) incidence, and overall response rate (ORR). Dose escalation (Part 1) and expansion (Part 2) in MM pts is complete, and enrollment into a lymphoma cohort is ongoing. GSK2857916 is dosed once every 3 weeks as a 1-hr intravenous infusion, without required prophylaxis for infusion-related reactions (IRR). Eligible MM pts must have been treated with alkylators, proteasome inhibitors (PI), immunomodulators (IMiDs), and stem cell transplantation (if eligible) and must have documented progression on or within 60 days of last therapy. Pts remain on treatment until progression, unacceptable toxicity, consent withdrawal, or completing 16 treatment cycles. All pts received steroid eye drops for 4 days with each infusion to mitigate corneal events. Results Part 1 results (N=38) were previously presented (Blood, 2016 128:1148); no maximum tolerated dose was identified and the RP2D was determined to be 3.4 mg/kg. Part 2 enrolled 35 MM pts treated at the RP2D: median age is 60 years (range 46-75) and 49% are male. Fifty-seven percent received ≥5 prior lines of therapy (range 1- & gt;10). All pts received and 97% were refractory to PI, all pts received and 91% were refractory to IMiDs, 40% received and 37% were refractory to daratumumab, and 89% were double-refractory to PI and IMiDs. Median number of infusions was 5 (range 1-13) and 54% of pts received ≥5 infusions. The ORR for Part 2 was 60% (21/35; 95% CI 42.1-76.1), including 1 sCR, 2 CR, 15 VGPR, and 3 PR. The ORR in pts previously treated with daratumumab was 43% (6/14; 95% CI 17.7-71.1). Median duration of response was not reached, with a median PFS of 7.9 months (95% CI 3.1- NA). All pts had at least 1 adverse event (AE); the most frequent (≥25%) regardless of cause were corneal events (63%), thrombocytopenia/platelet count decreased (57%), anemia (29%), AST increased (29%), and cough (26%). Corneal events (most frequent ≥20%: vision blurred, dry eye, photophobia) were mostly Grade (Gr) 1/2 and were reversible. Gr 3/4 AEs reported in ≥10% of pts were thrombocytopenia/platelet count decreased (34%) and anemia (14%). Serious AEs were reported in 40% (14/35) of pts. With no pre-medication, 8 pts had IRRs (2 Gr 1, 3 Gr 2, 3 Gr 3) that occurred with the first infusion, resolved, and did not recur with subsequent infusions. A total of 18 pts discontinued treatment for disease progression (n=15), AE (n=2; thrombocytopenia, CPK elevation), or pts decision (n=1); 17 pts are ongoing. Conclusion GSK2857916 monotherapy demonstrated encouraging single agent activity with an ORR of 60%, and deep (51% ≥VGPR) and durable responses in heavily pre-treated relapsed/refractory MM pts who have limited treatment options. The target and therapeutic mechanisms of action differentiate GSK2857916 from currently approved drugs in MM. Results show a manageable safety profile, with thrombocytopenia/platelet count decreased and low grade corneal events being the most frequently reported AEs and most frequent reason for dose modifications. Detailed safety and clinical activity together with results from correlative analyses will be presented. Study is funded by GlaxoSmithKline (NCT02064387); drug linker technology is licensed from Seattle Genetics; monoclonal antibody is produced using POTELLIGENT ® Technology licensed from BioWa. Disclosures Trudel: Astellas: Research Funding; Janssen: Research Funding; Takeda: Honoraria; GlaxoSmithKline: Research Funding; Celgene: Consultancy, Honoraria; Amgen: Consultancy, Honoraria. Lendvai: GlaxoSmithKline: Research Funding. Popat: Celgene: Honoraria, Other: Travel support for meetings; Amgen: Honoraria; Takeda: Honoraria, Other: Travel support for meetings; Janssen: Honoraria, Other: Travel support for meetings. Voorhees: Janssen: Consultancy, Speakers Bureau; Amgen: Speakers Bureau; Celgene: Consultancy, Speakers Bureau; Bristol-Myers Squibb: Consultancy; Novartis: Consultancy; Takeda: Consultancy; Oncopeptides: Consultancy. Richardson: Takeda: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Oncopeptides AB: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Anderson: Celgene, Takeda, and Amgen: Speakers Bureau. Sutherland: Janssen: Honoraria. Yong: Janssen: Honoraria, Research Funding; Amgen: Honoraria, Research Funding. Hoos: Imugene: Equity Ownership; GlaxoSmithKline: Employment, Equity Ownership. Gorczyca: GlaxoSmithKline: Employment, Equity Ownership. Lahiri: GlaxoSmithKline: Employment, Equity Ownership. He: GlaxoSmithKline: Employment, Equity Ownership. Jewell: GlaxoSmithKline: Employment, Equity Ownership. Opalinska: GlaxoSmithKline: Employment, Equity Ownership. Cohen: Bristol Meyers Squibb: Consultancy, Research Funding; GlaxoSmithKline: Consultancy; Celgene: Consultancy; Janssen: Consultancy.

Abstract: Abstract 207 Introduction: Chemoimmunotherapy regimens have become the treatment standard for patients with CLL. Ofatumumab is a human monoclonal antibody that targets a unique small-loop epitope on CD20 and elicits rapid and efficient in vitro complement-dependent cytotoxicity, as well as antibody-dependent cellular cytotoxicity. Recent studies demonstrated single-agent ofatumumab activity, with high overall response rates (ORR) in patients with refractory CLL. We conducted an international, randomized, parallel group, Phase II trial with two doses of ofatumumab combined with fludarabine and cyclophosphamide (FC) in previously untreated patients with CLL to evaluate the efficacy and tolerability of this chemoimmunotherapy regimen. Methods: Previously untreated patients (N=61) with active CLL (by NCI-WG guidelines) were randomized to receive ofatumumab 500 mg (Group A) or 1000 mg (Group B) on day 1, combined with fludarabine (25 mg/m2 IV daily; days 1–3) and cyclophosphamide (250 mg/m2 IV daily; days 1–3) every 4 weeks for a total of 6 courses. In both Groups, the first dose of ofatumumab was 300 mg. Dose reduction of FC, but not ofatumumab, was allowed. Premedication for ofatumumab was paracetamol and antihistamine prior to each infusion, and glucocorticoid prior to infusions 1 and 2. Neutrophil growth factor and anti-infective prophylaxis were not mandated. The primary endpoint was complete response (CR) rate (1996 NCI-WG criteria) assessed by an Independent Review Committee (IRC), measured from the start of treatment until 3 months after the last infusion. Safety evaluations included investigator-reported adverse events (AEs) and deaths. Follow-up continues for collection of time-to-event endpoints. Results: Data from all 61 patients were available for response assessment (primary endpoint). Pretreatment characteristics are shown in the Table. 71% and 57% of patients in Groups A and B, respectively, completed all 6 courses of O-FC treatment. The CR rate (95% CI) by IRC evaluation was 32% (17, 51%) for Group A and 50% (31, 69%) for Group B; the ORR (95% CI) was 77% (59, 90%) and 73% (54, 88%), respectively (Table). The median progression-free survival has not been reached with the short median follow up of 8 months. No CTC grade 3–4 infusion-related reactions on the day of ofatumumab infusion were reported. During treatment and up to 30 days following the last dose, the most common ( 〉 10% of patients) grade 3–4 AEs reported by investigators were infections in 11 patients (Group A, n=4; Group B, n=7) including febrile neutropenia in 3 patients in each Group, and hematologic AEs including neutropenia in 29 patients (Group A, n=11; Group B, n=18), anemia in 8 patients (Group A, n=2; Group B, n=6) and thrombocytopenia in 9 patients (Group A, n=2; Group B, n=7); grade 3–4 hemolytic anemia occurred in 2 patients in Group A and 1 in Group B; one patient in Group B died (19 days from last dose) with dyspnea (etiology unknown). Beyond the AE reporting period mentioned above, one patient in Group A died (50 days from last dose) due to febrile neutropenia during the follow up period. Results from additional analysis of data will be presented at the meeting. Conclusions: The O-FC regimen is highly active in previously untreated patients with CLL at both ofatumumab doses investigated and may offer a new chemoimmunotherapy treatment option in these patients. AEs with the O-FC regimen were manageable with no unexpected toxicities. The 1000 mg dose of ofatumumab is currently being evaluated in combination with chemotherapy in other studies for patients with CLL. Disclosures: Wierda: Genmab, GlaxoSmithKline: Honoraria, Research Funding. Off Label Use: Ofatumumab is an investigational anti-CD20 monoclonal antibody, currently under development for the treatment of B-cell malignancies (chronic lymphocytic leukemia, diffuse large B-cell lymphoma, Waldenstroms macroglobulinemia and follicular lymphoma) as well as autoimmune diseases (rheumatoid arthritis and multiple sclerosis). Kipps:Physicians' Education Resource, Educational Concepts: Speakers Bureau; Genmab, Abbott Industries, Celgene, Biogen Idec, Cephalon, sanofi-aventis, Medimmune, Memgem, Genentech: Research Funding. Dürig:GlaxoSmithKline: Honoraria. Griskevicius:GlaxoSmithKline, Genmab: Research Funding. Stilgenbauer:GlaxoSmithKline, Genmab: Consultancy, Honoraria, Research Funding. Mayer:GlaxoSmtihKline: Consultancy. Smolej:Bayer Schering: Honoraria. Padmanabhan:GlaxoSmithKline: Consultancy, Honoraria; Celgene, Genentech: Consultancy. Gorczyca:GlaxoSmithKline: Employment. Chan:GlaxoSmithKline: Employment. Gupta:GlaxoSmithKline: Employment. Andersen:H. Lundbeck A/S: Shares ownership; Novo Nordisk A/S, H. Lundbeck A/S and Genmab A/S: Consultancy. Strange:Genmab: Employment. Nielsen:Genmab: Employment. Russell:Genmab: Employment, Equity Ownership.

Abstract: Abstract 921 Background: Patients with chronic lymphocytic leukemia (CLL) refractory to fludarabine and alemtuzumab (FA-ref) or refractory to fludarabine with bulky ( 〉 5 cm) lymphadenopathy (BF-ref) have poor prognosis with salvage regimens (Tam et al. Leuk Lymphoma 2007). Ofatumumab, a human CD20 monoclonal antibody, was recently approved by the US FDA and EMEA for treatment of CLL refractory to fludarabine and alemtuzumab based on the interim analysis of the pivotal international clinical trial, which included data from 138 patients with FA-ref and BF-ref CLL. At the interim analysis, the overall response rate (ORR; primary endpoint) with single-agent ofatumumab was 58% (99% CI: 40, 74) in the FA-ref group and 47% (99% CI: 32, 62) in the BF-ref group (Wierda et al. J Clin Oncol 2010). Here, we report the final result for the primary endpoint in 206 patients with FA-ref or BF-ref CLL enrolled in this study. Methods: Patients with FA-ref or BF-ref CLL received 8 weekly doses of ofatumumab followed by 4 monthly doses (dose 1, 300 mg; doses 2–12, 2000 mg). Premedication included acetaminophen, antihistamine and glucocorticoid. The primary endpoint (ORR, 1996 NCI-WG criteria) was evaluated over the 24-week treatment period by an Independent Endpoint Review Committee (IRC). Secondary endpoints included duration of response, progression-free survival (PFS), overall survival (OS) and safety. Results: Baseline characteristics are summarized in the Table; 89% and 50% of patients completed 8 and 12 ofatumumab doses, respectively. The ORR (95% CI) by IRC evaluation was 51% (40, 61) for the FA-ref group and 44% (35, 64) for the BF-ref group. Two patients in the BF-ref group achieved complete remission (Table). Results for time-to-event analyses are shown in the Table. Infusion-related AEs occurred in 63% of patients, which primarily occurred during doses 1 and 2, and diminished with subsequent doses. Infusion-related reactions were grade 1–2 events in 95% of patients; no fatal reactions were reported. The most common (≥5% of all patients) grade ≥3 adverse events (AEs) that occurred from start of treatment until 30 days after the last infusion were infections (24%), neutropenia (12%) and anemia (5%). The most common grade ≥3 infection was pneumonia (8% of patients). Fatal infections occurred in 8% of patients (13% in FA-ref; 5% in BF-ref groups). Grade 3–4 thrombocytopenia occurred in 8 patients (4%), febrile neutropenia in 4 patients (2%) and autoimmune hemolytic anemia in 2 patients (1%). Early death (within 8 weeks from start of treatment) occurred in 5 patients (5%) in the FA-ref group (infections, n=5) and 4 patients (4%) in the BF-ref group (infections, n=2; myocardial infarction, n=1; pulmonary edema, n=1). Conclusions: These final results from the pivotal trial clearly demonstrate the efficacy and safety of ofatumumab monotherapy in this heavily pretreated patient population with FA-ref and BF-ref CLL. Additional data analyses are ongoing, and efficacy outcomes for patient subgroups will be presented. Disclosures: Wierda: GlaxoSmithKline: Honoraria, Research Funding. Kipps:GlaxoSmithKline: Research Funding. Mayer:GlaxoSmithKline: Consultancy, Research Funding. Robak:GlaxoSmithKline: Consultancy, Honoraria, Research Funding; Genmab: Consultancy, Research Funding; Roche: Consultancy, Honoraria, Research Funding. Furman:GlaxoSmithKline: Consultancy, Speakers Bureau; Genentech: Consultancy, Speakers Bureau; Cephalon, Inc.: Speakers Bureau; Celegene: Consultancy; Calistoga: Consultancy. Stilgenbauer:Amgen: Research Funding; Bayer: Consultancy, Honoraria, Research Funding; Boehringer-Ingelheim: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Genzyme: Consultancy, Honoraria, Research Funding; GSK: Consultancy, Honoraria, Research Funding; Mundipharma: Consultancy, Honoraria, Research Funding; Roche: Consultancy, Honoraria, Research Funding; Sanofi Aventis: Research Funding. Cartron:GlaxoSmithKline: Honoraria; Roche: Honoraria. Padmanabhan:GlaxoSmithKline: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Chan:GlaxoSmithKline: Employment. Gupta:GlaxoSmithKline: Employment. Gorczyca:GlaxoSmithKline: Employment. Davis:GlaxoSmithKline: Employment. Losic:Genmab A/S: Employment, Equity Ownership. Lisby:Genmab A/S: Employment. Österborg:GlaxoSmithKline: Consultancy, Honoraria, Research Funding; Genzyme: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Merck KGaA: Research Funding.