Fong, Abraham

Abstract Background: Colorectal cancer (CRC) is the third most common cancer in the United States. Aberrant activation of the Wnt signaling pathway is associated with CRC progression. Ring finger protein 43 (RNF43) is a single-pass type 1 transmembrane protein and a key feedback regulator of Wnt. SC-006 is a RNF43 targeted antibody drug conjugate, linked to a pyrrolobenzodiazepine dimer DNA crosslinking agent. Budigalimab (ABBV-181) is a PD-1 targeting, humanized, recombinant immunoglobulin G1 monoclonal antibody with Fc mutations (L234A, L235A) shown to reduce Fc receptor interactions and limit effector function. This open-label, Phase 1 clinical trial assessed the safety and efficacy of SC-006 as monotherapy and in combination with budigalimab in patients with CRC (NCT03035279). Methods: Evaluable patients had histologically or cytologically confirmed advanced metastatic or unresectable CRC. The trial consisted of 2 parts: part A (SC-006-monotherapy, 2 to 12 µg/kg, IV) and part B (SC-006 in combination with budigalimab at a fixed dose of 375 mg/kg IV every 3 weeks [Q3W]). Efficacy was assessed per RECIST 1.1 by radiographic assessments. Results: As of April 2019, 29 patients were enrolled (n=20 in part A and n=9 in part B). All patients experienced at least one treatment-emergent adverse event (TEAE). The most common TEAEs (>20% of patients) are summarized in Table 1. Two patients (7%) had dose-limiting toxicities of grade 4 thrombocytopenia. All 29 patients discontinued from the study, with study drug being discontinued for 76% of patients due to progressive disease. One death occurred in part A due to gastrointestinal hemorrhage with possible relation to SC-006. Serious TEAEs occurred in 8 patients (28%); these included thrombocytopenia and malignant neoplasm progression in 2 patients (7%) each. Progressive disease occurred in 18 patients (62%), stable disease was reported in 10 patients (34%) and the response for 1 patient was not reported. Conclusion: SC-006 dose escalation was limited by thrombocytopenia observed below the predicted efficacious dose, leading to study termination. Table 1.Summary of the Most Common Treatment-Emergent Adverse EventsPart A: SC-006-monotherapyPart B: SC-006+budigalimabTEAEs (>20% patients), n (%)2 ug/kg4 ug/kg8 ug/kg4 ug/kg8 ug/kg12 ug/kg4 ug/kg Q6W+budigalimab8 ug/kg Q6W+budigalimabOverallQ3WQ3WQ3WQ6WQ6WQ6W(N=1)(N=3)(N=1)(N=2)(N=10)(N=3)(N=4)(N=5)(N=29)Thrombocytopenia01 (33)1 (100)1 (50)4 (40)3 (100)1 (25)4 (80)15 (52)Fatigue0001 (50)3 (30)2 (67)3 (75)3 (60)12 (41)Nausea0001 (50)5 (50)1 (33)2 (50)2 (40)11 (38)Edema peripheral01 (33)01 (50)4 (40)02 (50)1 (20)9 (31)Decreased appetite01 (33)01 (50)4 (40)002 (40)8 (28)Dyspnea00004 (40)3 (100)01 (20)8 (28)Vomiting0001 (50)3 (30)1 (33)2 (50)1 (20)8 (28)Constipation0001 (50)3 (30)01 (25)2 (40)7 (24) Citation Format: Katrina S. Pedersen, Amit Mahipal, Andrea Cercek, Susanna Ulahannan, Michael Rossi, Abraham Fong, Daniel Brickman, Johanna Bendell. First-in-human clinical trial of SC-006, a RNF43 targeted antibody-drug conjugate, as a monotherapy and in combination with budigalimab in patients with advanced colorectal cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT167.

Abstract Background Brentuximab vedotin (BV) is an antibody-drug conjugate directed against CD30, a receptor that engages the CD30 ligand expressed on immune cells in the tumor microenvironment, promoting tumor cell growth (Montanari 2014, Hansen 2014). Through disruption of the microtubule network, BV induces apoptotic cell death, and may initiate an antitumor immune response (i.e., immunogenic cell death) through the induction of endoplasmic reticulum (ER) stress (Gardai 2015). Nivolumab is a fully human monoclonal PD-1 blocking antibody that prevents tumor immune evasion. Both agents have independent high single-agent response rates in patients (pts) with relapsed or refractory (R/R) Hodgkin lymphoma (HL), and when used in combination, may exhibit mechanistic synergy. Given the demonstrated efficacy of both BV and nivolumab, together these agents could yield improved CR rates prior to ASCT in pts with R/R HL, and potentially better long-term outcomes. Methods A phase 1/2 study is ongoing to evaluate the safety and antitumor activity of BV administered in combination with nivolumab as first salvage therapy in pts with R/R classical HL after standard frontline chemotherapy (NCT02572167). Adult pts are treated in 21-day cycles for up to 4 cycles (12 weeks). Pts receive 1.8 mg/kg BV on Cycle 1 Day 1, and 3 mg/kg nivolumab on Cycle 1 Day 8. For cycles 2 through 4, BV and nivolumab are administered on Day 1 of each cycle at the same doses. After completion of the Cycle 4 response assessment, pts are eligible to undergo ASCT. Investigator assessment of lymphoma response and progression is per the Lugano Classification Revised Staging System for malignant lymphoma (Cheson 2014). Results Twenty-five pts (60% female) with a median age of 32 years (range, 18-69) have been enrolled to date. Sixty percent of pts have relapsed disease, 36% have primary refractory disease (failure to achieve CR with frontline therapy, or relapse within 3 months of completing frontline therapy), and 1 pt (4%) has unknown status. At the time of enrollment, 32% of pts presented with extranodal disease and 16% with bulky disease. At the time of the data extract, 23 pts had received treatment. An increased incidence of infusion-related reactions (IRRs) was observed at the start of combination treatment in Cycle 2 during the BV infusion leading to 1 dose delay. Premedication with corticosteroids (hydrocortisone 100 mg or equivalent) and antihistamines at Cycles 2-4 was instituted through a protocol amendment. Six pts have completed combination treatment, and all have achieved an objective response (ORR, 100%), with 3 of 6 achieving a complete metabolic response (CmR, 50%). All 6 pts have proceeded directly to ASCT. Median number of CD34+ cells collected was 12.9 x106 cells/kg (range, 5-26) in a mean number of 1.7 apheresis sessions (range, 1-2). Adverse events (AEs) for all pts are summarized prior to ASCT. Eighteen of the 23 treated pts (78%) experienced adverse events (AEs). Fifteen pts (65%) had AEs ≤ Grade 2 in severity and 3 pts (13%) experienced Grade 3 AEs. No pts experienced Grade 4 AEs pre-ASCT. Fatigue was the most common AE occurring in 35% of pts, followed by nausea (26%), rash (22%), dyspnea, myalgia, and pruritus (17% each). One pt experienced a treatment-related serious adverse event (SAE) of dehydration, hypercalcemia, and acute kidney injury. Immune-related adverse events (IrAEs) were experienced by 3 pts; 2 pts who experienced Grade 1 rash treated with topical steroids, and 1 pt who experienced Grade 1 hypothyroidism. No pts have discontinued treatment prematurely. In addition to Reed-Sternberg cells, CD30 is expressed on activated T cells. Preliminary biomarker data indicate a BV-induced decrease in the percentage of CD4+ T regulatory (Treg) cells at C1D8, with no decrease in proliferating CD8+ T cells, and no significant decrease observed in the percentage of CD4+ Th1 cells compared to baseline for 5 of 6 pts (83%). Nivolumab induced a robust expansion of T cells at C1D15. Conclusions Early data suggest the combination of BV and nivolumab is an active and well-tolerated salvage therapy in pts with R/R HL. While an elevated incidence of IRRs has been observed, toxicities with this regimen appear to be tolerable overall. The preliminary antitumor activity suggests this combination may be a promising option for R/R HL pts. Updated results will be shared at the time of presentation. Disclosures Herrera: Pharmacyclics: Research Funding; Merck: Research Funding; Immune Design: Research Funding; Genentech: Research Funding; Adaptive Biotechnologies: Research Funding; Seattle Genetics: Research Funding. Bartlett:Gilead: Consultancy. Moskowitz:BMS: Honoraria, Research Funding; Seattle Genetics: Honoraria, Research Funding. Feldman:Abbvie/Pharmacyclics/Janssen: Speakers Bureau; Seattle Genetics: Consultancy, Research Funding, Speakers Bureau; Celgene: Consultancy, Speakers Bureau. LaCasce:Seattle Genetics: Research Funding; Forty Seven Inc.: Consultancy. Ansell:Bristol Myers Squibb: Research Funding; Seattle Genetics: Research Funding; Celldex: Research Funding; Affimed: Research Funding. Fenton:Seattle Genetics: Employment, Equity Ownership. Kato:Bristol-Myers Squibb: Employment. Fong:Seattle Genetics: Employment, Equity Ownership.

Abstract Background: Classical Hodgkin lymphoma (HL) is characterized by the presence of CD30-positive Hodgkin Reed-Sternberg cells. The standard of care for patients (pts) with relapsed or refractory (R/R) HL is salvage chemotherapy followed by high dose chemotherapy and autologous stem cell transplant (auto-SCT). Approximately 50% of these pts will experience relapse or progression of HL after auto-SCT. For these individuals, outcomes have historically been poor, with median overall survival (OS) from time of relapse ranging from 10.5 to 27.6 mos (Crump, 2008; Fanale, 2013). A pivotal phase 2 study evaluated brentuximab vedotin, a CD30-directed antibody-drug conjugate, in pts with R/R HL after auto-SCT (ClinicalTrials.gov #NCT00848926). Primary results and 3-year follow-up data have been previously reported (Younes, 2012; Gopal, 2015). Here, we summarize final data from the 5-year follow-up period. Methods: Pts received 1.8 mg/kg brentuximab vedotin once every 3 wks as a 30-min outpatient IV infusion for up to 16 cycles. The primary endpoint was the objective response rate (ORR) per independent review according to the Revised Response Criteria for Malignant Lymphoma (Cheson 2007). Assessments of response and durability of response per an independent review facility (IRF) have been previously reported. Following a protocol amendment that removed the requirement for routine CT scanning during the follow-up period, disease status was only assessed per the investigator. Survival and disease status were assessed every 3 mos for 2 yrs and then every 6 mos through Year 5. CT scans were required if progression was suspected clinically. At the time of the amendment, 18 patients were still being assessed for progression; these patients had been in long-term follow-up for a median of over 30 months. Results: The enrolled population of 102 pts (53% female) was heavily pretreated and had a median age of 31 yrs (range, 15-77 yrs). Pts received a median of 9 cycles (range, 1-16) of brentuximab vedotin. Per investigator, the ORR to brentuximab vedotin was 72% and complete remission (CR) rate was 33%. The most common treatment-related adverse events were peripheral sensory neuropathy, nausea, fatigue, neutropenia, and diarrhea. Adverse events of Grade 3 or higher that occurred in ≥5% of pts were neutropenia, peripheral sensory neuropathy, thrombocytopenia, and anemia. At study closure, which occurred approximately 5 yrs after the last patient's end-of-treatment visit, the median observation time for all enrolled patients from first dose was 35.1 mos (range, 1.8 to 72.9). The estimated 5-year overall survival rate was 41% (95% CI: 31 %, 51%) and the median OS was 40.5 mos (95% CI: 28.7, 61.9 [range, 1.8 to 72.9+]). Median OS by best clinical response was CR (n=34): median not reached; partial remission (PR, n=39): 39.4 mos; and stable disease (SD, n=28): 18.3 mos. The median PFS was 9.3 months overall, but was not reached in CR pts. Of the 102 enrolled patients, 15 remained in follow-up and in remission at study closure. Among these 15 pts, 6 received consolidative allo-SCT and 9 have received no further therapy since completing brentuximab vedotin. Conclusions: These end-of-study results demonstrate that single agent brentuximab vedotin can induce durable remissions and long-term survival in a subset of heavily pretreated patients with relapsed/refractory HL, particularly in pts that achieve CR. A randomized phase 3 study is being conducted to evaluate brentuximab vedotin in combination with AVD (doxorubicin, vinblastine, and dacarbazine) versus ABVD (A, bleomycin, VD) for frontline treatment of advanced HL (ECHELON-1 trial, ClinicalTrials.gov #NCT01712490). Figure 1. Overall Survival Figure 1. Overall Survival Disclosures Chen: Seattle Genetics: Consultancy, Research Funding; Genentech: Consultancy; Gilead: Consultancy; Janssen: Consultancy. Gopal:BMS: Research Funding; Piramal: Research Funding; Emergent/Abbott: Research Funding; Millenium: Honoraria, Research Funding; Janssen: Consultancy; Spectrum: Consultancy, Research Funding; BioMarin: Research Funding; Seattle Genetics: Consultancy, Honoraria; Gilead: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Sanofi-Aventis: Honoraria; Merck: Research Funding. Smith:Seattle Genetics: Research Funding; Celgene: Consultancy, Speakers Bureau. Ansell:Bristol-Myers Squibb: Research Funding; Celldex: Research Funding. Rosenblatt:Seattle Genetics: Research Funding. Savage:Seattle Genetics: Honoraria, Speakers Bureau; BMS: Honoraria; Infinity: Honoraria; Roche: Other: Institutional research funding. Connors:Roche: Research Funding; Seattle Genetics: Research Funding. Engert:Takeda Millenium: Honoraria, Research Funding; Seattle Genetics: Honoraria, Research Funding. Larsen:Seattle Genetics Inc.: Employment, Equity Ownership. Huebner:Takeda Pharmaceuticals International Co.: Employment, Equity Ownership. Fong:Seattle Genetics, Inc.: Employment, Equity Ownership. Younes:Janssen: Honoraria; Novartis: Research Funding; Incyte: Honoraria; Takeda Millenium: Honoraria; Celgene: Honoraria; Bristol Meyer Squibb: Honoraria; Curis: Research Funding; Bayer: Honoraria; Seattle Genetics: Honoraria, Research Funding; Sanofi-Aventis: Honoraria; Johnson and Johnson: Research Funding.

Key Points A total of 38% of patients who achieved CR (13 of 34) on brentuximab vedotin have remained in remission for >5 years and may be cured. Nine of the 13 patients (9% of all enrolled patients) have remained in long-term remission without a consolidative allogeneic transplant.