REGULAR ARTICLE Phase 1b study of the BET protein inhibitor RO6870810 with venetoclax and rituximab in patients with diffuse large B-cell lymphoma Michael Dickinson,1,2 Javier Briones,3,4 Alex F. Herrera,5 Eva Gonzalez-Barca,6 Nilanjan Ghosh,7 Raul Cordoba,8 Sarah C. Rutherford,9 Eirini Bournazou, Emily Labriola-Tompkins, Izolda Franjkovic, Evelyne Chesne,12 Jurriaan Brouwer-Visser,10 Katharina Lechner,11 10 10 11 Barbara Brennan,10 Eveline N€ uesch,12 Mark DeMario,10 Dominik R€ uttinger,11 Martin Kornacker,12 and Martin Hutchings13,14 1 Clinical Haematology, Peter MacCallum Cancer Centre and Royal Melbourne Hospital, Melbourne, VIC, Australia; 2Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, VIC, Australia; 3Hematology Department, Hospital de la Santa Creu i Sant Pau, Sant Pau, Spain; 4Jose Carreras Leukemia Research Institutes, Autonomous University of Barcelona, Barcelona, Spain; 5Department of Hematology and Hematopoietic Cell Transplantation, City of Hope National Medical Center, Duarte, CA; 6 Department of Hematology, Institut Catala d'Oncologia, Hospital duran i Reynals, Institut d'Investigaci o Biom edica de Bellvitge (IDIBELL), Universitat de Barcelona, L’Hospitalet de LLobregat, Barcelona, Spain; 7Department of Hematologic Oncology and Blood Disorders, Levine Cancer Institute, Atrium Health, Charlotte, NC; 8Department of Hematology, Fundacion Jimenez Diaz University Hospital, Madrid, Spain; 9Meyer Cancer Center, Division of Hematology and Medical Oncology, Weill Department of Medicine, NewYork-Presbyterian Hospital, Weill Cornell Medicine, New York, NY; 10Roche Innovation Center New York, Roche Pharma Research and Early Development, New York, NY; 11 Roche Innovation Center Munich, Roche Pharma Research and Early Development, Penzberg, Germany; 12Roche Innovation Center Basel, Roche Pharma Research and Early Development, Basel, Switzerland; 13Department of Hematology and 14Phase 1 Unit, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark Key Points Bromodomain and extraterminal (BET) proteins are transcriptional activators for multiple oncogenic processes in diffuse large B-cell lymphoma (DLBCL), including MYC, BCL2, E2F, and  BET inhibitor toll-like receptor signaling. We report results of a phase 1b dose-escalation study of the novel, RO68708101veneto- subcutaneous BET inhibitor RO6870810 (RO) combined with the BCL-2 inhibitor venetoclax, clax1rituximab has a and rituximab, in recurrent/refractory DLBCL. RO was delivered for 14 days of a 21-day cycle, manageable safety whereas venetoclax was delivered continuously. A 3 1 3 escalation design was used to deter- profile in relapsed/ refractory diffuse large mine the safety of the RO1venetoclax doublet; rituximab was added in later cohorts. Thirty- B-cell lymphoma. nine patients were treated with a median of 2.8 cycles (range, 1-11). Dose-limiting toxicities included grade 3 febrile neutropenia, grade 4 diarrhea, and hypomagnesemia for the doublet;  A clinically relevant and grade 3 hyperbilirubinemia and grade 4 diarrhea when rituximab was added. The doublet signal of antitumor maximum tolerated dose (MTD) was determined to be 0.65 mg/kg RO1600 mg venetoclax; for activity serves as a proof of principle for RO1venetoclax1rituximab, the MTDs were 0.45 mg/kg, 600 mg, and 375 mg/m2, respectively. this combination, The most frequent grade 3 and 4 adverse events were neutropenia (28%) and anemia and warranting further thrombocytopenia (23% each). Responses were seen in all cohorts and molecular subtypes. study. Sustained decreases in CD11b on monocytes indicated pharmacodynamic activity of RO. Over- all response rate according to modified Lugano criteria was 38.5%; 48% of responses lasted for $180 days. Complete response was observed in 8 patients (20.5%). Optimization of the treat- ment schedule and a better understanding of predictors of response would be needed to sup- port broader clinical use. This trial is registered on www.clinicaltrials.gov as NCT03255096. Introduction Bromodomain and extraterminal (BET) proteins have been implicated in malignant transformation and in resistance to anticancer therapy.1 Preclinical studies support the strategy of inhibiting the interaction Submitted 2 March 2021; accepted 27 June 2021; prepublished online on Blood Advan- ß 2021 by The American Society of Hematology. Licensed under Creative Commons ces First Edition 28 September 2021; final version published online 22 November 2021. Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), DOI 10.1182/bloodadvances.2021004619. permitting only noncommercial, nonderivative use with attribution. All other rights For original data, please contact martin.kornacker@roche.com. reserved. The full-text version of this article contains a data supplement. 4762 23 NOVEMBER 2021 • VOLUME 5, NUMBER 22 between BET proteins and acetylated lysine to achieve antitumor of RO (0.3-0.65 mg/kg subcutaneously (SC) on days 1 to 14 of effects. Direct-acting BET inhibitors use acetyl-lysine competitive 21-day cycles) in a standard 3 1 3 design. RO was combined with binding to displace BET proteins from chromatin, resulting in pre- venetoclax, which was administered orally starting at a dose of 400 clinical activity in a variety of tumor models.2 The selectivity of these mg once a day with subsequent investigation of 600 and 800 mg compounds for transformed cells arises from the localization of BET doses for additional cohorts, with RO (supplemental Figure 1). proteins to superenhancers that regulate cell-specific and onco- Patients were treated until disease progression, unacceptable toxic- genic transcriptional programs, including those governed by the ities or withdrawal from treatment for other reasons, or death. oncogene encoding the transcription factor MYC.1 In addition to Once the MTD/maximum dose administered was determined, addi- MYC downregulation, BET inhibition has been shown to decrease tional patients were enrolled to receive the recommended doses of oncogenic nuclear factor-B activity, decrease expression of ERK1/2, RO and venetoclax in combination with rituximab at a dose of 375 programmed death-ligand 1, CXCL12, and BCL2, thereby affecting mg/m2 bovine serum albumin administered IV every week during the immunity, cancer cell metastasis.3-8 and lymphoma proliferation.9 first cycle and on day 1 of all cycles thereafter. Patients with diffuse large B-cell lymphoma (DLBCL) that has relapsed or refractory (R/R) to first-line therapies or who are not Patients eligible for study inclusion had DLBCL and/or HGBL-DH/ candidates for high-dose therapy with autologous stem cell trans- TH, R/R to first-line or subsequent therapies, who had received at plantation (ASCT), and those with high-grade B-cell lymphoma with least 1 prior chemotherapy regimen that included an anti-CD20 tar- MYC and BCL2 and/or BCL6 rearrangements (HGBL-DH/TH) rep- geting agent, with no curative option. Patients were relapsed or resent a poor-prognosis group and a high unmet clinical need.10,11 refractory to $1 course of chemotherapy, including an anti-CD20 Similarly, double-expressor DLBCLs (DE-DLBCLs), characterized by monoclonal antibody, and were not eligible for ASCT (including higher protein expression of MYC and BCL2, seem to be associ- those with chemorefractory disease). Patients with transformed follic- ated with lower rates of response and poorer survival after upfront ular lymphoma (FL) were eligible, provided DLBCL or HGBL-DH/TH R-CHOP.12,13 Preclinical studies using BET inhibitor JQ1 in DLBCL histology was biopsy confirmed before study entry and a treatment models demonstrated potent, single agent in vivo activity. Clinical regimen as described had been administered. All patients were $18 responses among heavily pretreated patients with relapsed DLBCL years of age, had an Eastern Cooperative Oncology Group (ECOG) were observed in the phase 1 First in Man (FiM) monotherapy trial performance status #1, and had acceptable organ function. Life of the BET inhibitor RO6870810 (RO; NCT01987362).14 Partial expectancy was at least 3 months. This study was approved by local responses (assessed by Lugano criteria15) were noted among institutional review boards and conducted in accordance with the patients with both MYC and MYC1BCL2 double-expression phe- protocol, Good Clinical Practice standards, and the Declaration of notype disease. BET protein inhibitors such as RO therefore may Helsinki. All enrolled patients gave written informed consent. offer novel therapeutic options in DLBCL, double-expression lym- Safety assessments phoma, and HGBL-DH/TH. However, compared with the adminis- tration as a single agent, rational combinations for BET inhibitors Patients were considered evaluable for safety if they had received may improve clinical activity. Venetoclax, a small-molecule BCL2 $1 injection of study drug. All adverse events (AEs) were graded inhibitor, has demonstrated single-agent responses in relapsed per the National Cancer Institute’s Common Terminology Criteria for DLBCL, but these were short lived.16 The coadministration of BCL2 Adverse Events, version 4.03. (venetoclax) and BET (JQ1) inhibitors produced the most potent DLTs were defined as AEs during cycle 1 that were at least possi- synergistic effects among combinations tested in cell lines express- bly related to the study drug and met 1 of the following National ing MYC and bcl-2 proteins (DE-DLBCL cell lines) and primary Cancer Institute’s Common Terminology Criteria (version 4.03) crite- patient-derived HGBL-DH models.17 Rituximab has been shown to ria: grade 4 neutropenia lasting $5 days or grade 3 or 4 neutrope- improve the efficacy of venetoclax in the setting of chronic lympho- nia with fever and/or infection; grade 4 thrombocytopenia (or grade cytic leukemia through sensitization of cells to apoptosis, and it 3 with bleeding); grade 4 anemia; grade 3 or 4 nonhematologic tox- does so with minimal additional toxicity. Nonoverlapping mecha- icity (excluding grade 3 vomiting and grade 3 diarrhea, including the nisms of action and toxicities of RO, venetoclax, and rituximab sug- clinical sequelae [eg, electrolyte abnormalities] occurring with sub- gest the possibility of enhanced activity when these agents are optimal prophylactic and curative treatment with either toxicity and coadministered in the clinic. The demonstration of potent synergy excluding alopecia); grade 3 or 4 skin ulceration or other skin and with BET and BCL2 inhibitors provides an additional compelling SC tissue disorders related to the SC injection of RO; or a dosing rationale.17 We present a phase 1b study that explored RO given delay .14 days caused by treatment-emergent AEs or related with venetoclax, with or without rituximab, in patients with R/R severe laboratory abnormalities. Grade #3 drug-related fever, skin, DLBCL and/or HGBL-DH/TH after standard first-line regimens. or SC tissue disorders localized at the site of injection including grade #3 rash, pruritus, skin induration, or pain of skin were not Materials and methods considered DLTs. Study design and participants The MTD was defined as the highest tested dose below the dose at which a DLT was observed in $2 patients. Study NP39461 (NCT03255096) was an open-label, dose-escala- tion study with the objective of evaluating safety and dose-limiting Changes in vital signs, physical examination and ECG findings, clini- toxicities (DLTs) and establishing the maximum tolerated doses cal laboratory results, and the incidence of anti-drug antibodies to (MTDs) or maximum dose administered of RO and venetoclax and rituximab (during and after combination administration of the recommended doses of RO and venetoclax to be RO1venetoclax and RO1venetoclax coadministered with rituximab) co-administered with rituximab. Patients received escalating doses were also assessed. 23 NOVEMBER 2021 • VOLUME 5, NUMBER 22 PHASE Ib STUDY OF BET INHIBITOR RO6870810 IN DLBCL 4763 Growth factors were prohibited within 7 days before enrollment but All authors had a role in analyzing the data and had access to the were allowed for treatment of cytopenias during the study. primary clinical trial data. Efficacy assessments Results Evaluation of the anticancer activity of RO was a secondary objec- tive, as measured by time to first and best response, overall Patient demographics and disposition response rate (ORR), progression-free survival (PFS), duration of Thirty-nine patients with R/R DLBCL were recruited into the study, response, and overall survival. and those who received at least 1 dose of study drug were evalu- able for safety and efficacy analysis (Table 1). Response assessment in patients with DLBCL was made by Inde- pendent Radiological Centre Review and followed the Lugano clas- Overall, the median age of patients was 65 years (range, 28-81 sification.15 Radiological assessment consisted of diagnostic years). Nineteen patients (48.7%) were male and 20 (51.3%) were computed tomography (CT) at baseline and then every 2 cycles female. The majority of patients were White (37 patients [94.9%]). (standard of care) and combined positron emission tomography Of the 39 enrolled patients, 19 patients (48.7%) had an Eastern (PET)-CT at baseline and then every 4 cycles or to confirm com- Cooperative Oncology Group (ECOG) score of 1, 18 patients plete remission (CR). (46.2%) had an ECOG score of 0, and the remaining 2 patients (5.1%) had an ECOG score of 2. Baseline disease characteristics Patients who received $1 injection of study drug, had $1 post- are presented in Table 1. Of note, patients had a mean of 3.3 prior baseline tumor assessment per Lugano classification criteria, and DLBCL treatments. Twenty-nine patients (74%) were refractory to had no major protocol deviations were considered evaluable for effi- the immediate prior therapy, and 72% of patients received the study cacy. Responders were defined as patients who achieved a con- treatment in ,3 months after the end of the prior therapy. All 39 firmed CR or partial response (PR). PFS was defined as the time patients discontinued the treatment by the time of data cutoff on 7 from the date of first study drug administration to the first date of November 2019; 10 patients (25.6%) reported AEs that led to objectively determined progressive disease or death from any cause. treatment discontinuation; 24 patients (61.5%) recorded progres- PFS was censored at the date of the most recent objective sive disease, symptomatic deterioration, or lack of efficacy as the progression-free observation for patients who were still alive at the primary reasons for discontinuing treatment; 1 patient (2.6%) with- time of analysis and without evidence of tumor progression. For drew from treatment; and 4 patients (10.3%) discontinued study patients who received subsequent anticancer therapy before objec- treatment because of other or unknown reasons. Patients com- tive disease progression or death, PFS was censored at the date of pleted a median of 2.8 treatment cycles (range, 1-11). the last objective progression-free observation before the date of subsequent therapy. Safety Pharmacokinetic parameters All 39 enrolled patients (100%) experienced at least 1 treatment- emergent AE. Blood samples were collected to evaluate concentrations of RO and were analyzed by validated methods. Multiple samples were The majority of patients experienced treatment-emergent grade $3 collected for assessment of RO on days 1 and 15 of cycle 1, and AEs (34 patients [87.2%]), or serious AEs (SAEs; 25 patients day 1 of subsequent even-numbered cycles. [64.1%]). Of those, 23 patients (59%) had related grade $3 AEs, and 11 (28.2%) had related SAEs (supplemental Table 1). Pharmacodynamics and biomarkers Five patients experienced 5 DLTs. DLTs occurred in cohort 3 (grade For the pharmacodynamic assessments, venous blood samples 3 febrile pneumonia; RO 0.45 mg/kg1venetoclax 600 mg), cohort were obtained weekly during cycle 1. The absolute number of 4 (grade 4 hypomagnesemia, grade 4 diarrhea; RO 0.45 mg/ CD11b1 cells within the CD141 positive monocyte population was kg1venetoclax 800 mg), and cohort 5A (grade 3 hyperbilirubinemia, assessed as a surrogate pharmacodynamic marker by flow cytome- grade 4 diarrhea; RO 0.65 mg/kg1venetoclax 600 mg1rituximab try, before and after the first administration of RO. 375 mg/m2). All DLTs were considered serious except for the DLT of hypomagnesemia (supplemental Table 1). The doublet MTD was Statistical methods determined to be 0.65 mg/kg RO1600 mg venetoclax, and the trip- Formal hypothesis testing was not performed for this phase 1b let MTD was 0.45 mg/kg RO1600 mg venetoclax1375 mg/m2 study. The sample size was based on a standard 3 1 3 dose- rituximab. escalation design and was considered sufficient to evaluate the safety and clinical activity of the combinations. AEs were coded The most common AEs (experienced by $30% patients) were using the current Medical Dictionary for Regulatory Activities, and injection site reaction (24 patients [61.5%]), diarrhea (23 patients [59.0%]), anemia and nausea (18 patients [46.2%] each), thrombo- safety and clinical efficacy were summarized by descriptive statis- cytopenia (13 patients [33.3%]), and neutropenia (12 patients tics. The 95% confidence interval (CI) for the objective response [30.8%]). AEs experienced by $15% of the patients are summa- rate was calculated using the Wilson’s score method with continuity rized in Table 2. correction, and PFS was analyzed using the Kaplan-Meier method. For the pharmacokinetic analyses, key exposure parameters such as The grade $3 AEs experienced by $10% of patients were neutro- maximum plasma concentration and area under the curve were sum- penia (11 patients [28.2%]); anemia and thrombocytopenia (9 marized with descriptive statistics. The study design with the differ- patients [23.1%]); hypokalemia (5 patients [12.8%]); and febrile ent dose cohorts is shown in Figure 1. neutropenia (4 patients [10.3%]; Table 3). 4764 DICKINSON et al 23 NOVEMBER 2021 • VOLUME 5, NUMBER 22 4000 0.3 mg RO 0.45 mg RO 0.6 mg RO 3000 2000 1500 1000 RO concentration (ng/ml) 500 70 10 0 20 40 0 20 40 0 20 40 Time after dose (hours) Figure 1. Concentration-time profiles for RO in combination with venetoclax across the dose range 0.3 to 0.65 mg/kg. Twelve (31%) patients received pegfilgrastim/filgrastim, 13 (33%) AEs leading to treatment discontinuation received blood transfusion, and 7 received (18%) platelets; 5 Ten patients (25.6%) had a total of 10 AEs leading to discontinua- (13%) patients received both. tion of the study treatment, with pneumonia (2 patients [5.1%]) The SAEs experienced by $5% of patients were pneumonia (4 being reported in .1 patient ($5%; supplemental Table 1). The patients [10.3%]), febrile neutropenia (3 patients [7.7%]), and diar- remaining of these AEs were reported in 1 patient each: hepatitis, rhea and pyrexia (2 patients [5.1%] in each PT). Eleven patients hyperbilirubinemia, thrombocytopenia, gastric hemorrhage, cranioce- (28.2%) experienced 17 SAEs considered related to the study rebral injury, hypomagnesaemia, anxiety, and pulmonary embolism. treatment by the investigator. The related SAEs experienced in .1 In 4 patients (10.2%), AEs leading to treatment discontinuation patient ($5%) were pneumonia and diarrhea (2 patients [5.1%] in were considered to be related to the study treatment by the each PT). investigator. Twenty-one deaths (53.8%) were reported in the study: 18 deaths (46.2%) due to progressive disease, 1 death due to AE (pneumo- Table 1. Baseline disease characteristics nia, considered unrelated to study drug by the investigator), 1 due Baseline characteristics Population (N 5 39) to disease relapse, and 1 due to an infusion reaction to a subse- Disease stage IV, n (%) 30/37 (81.1) quent treatment during the long-term follow-up period. Of the 21 deaths, 14 occurred in the long-term follow-up period, and 7 Transformed FL, n (%) 8/38 (21.5) occurred in the period before long-term follow-up. International Prognostic Index score, median (range) (n 5 36) 3 (0-4) Prior DLBCL treatments, mean (min-max) 3.3 (1-6) Pharmacokinetics CAR T, n (%) 2 (5.1) Plasma concentration-time profiles for RO administered in combina- Bispecific antibodies, n (%) 5 (12.8) tion with venetoclax or in combination with venetoclax and rituximab Interval between prior treatment and study treatment are presented in Figure 1. RO demonstrated rapid absorption #1 mo 11 (28.2) across dose levels. Maximum concentration was generally achieved within 1 hour (median, 0.5 hour). .1 mo and # 3 mo 17 (43.6) . 3 mo 11 (28.2) Pharmacodynamics Cell of origin, n (%) Chromatin immunoprecipitation sequencing previously identified a GCB 24/33 (72.7) strong BRD4-driven superenhancer near the CD11b promoter, and ABC 7/33 (21.2) displacement of bound BRD4 from the superenhancer element by a MYC1BCL2 DE-DLBCL, n (%) 10/18 (55.5) BET inhibitor resulted in diminished CD11b gene expression. In this MYC translocation, n (%) 1/30 (3.3) study, CD11b expression on peripheral blood mononuclear cells was measured by flow cytometry before the dose and at various BCL2 translocation, n (%) 9/30 (30.0) time points between days 1 and 15 of cycle 1. Treatment with RO 23 NOVEMBER 2021 • VOLUME 5, NUMBER 22 PHASE Ib STUDY OF BET INHIBITOR RO6870810 IN DLBCL 4765 Table 2. Treatment-emergent AEs by cohort, all grades, in $5% of patients Cohort 1 Cohort 2 Cohort 3 Cohort 3A Cohort 4 Cohort 5 Cohort 5A Total RO RO 0.45 mg/kg 0.65 mg/kg RO RO RO 1 venetoclax RO RO 1 venetoclax 0.30 mg/kg 0.45 mg/kg 0.45 mg/kg 600 mg 0.45 mg/kg 0.65 mg/kg 600 mg 1 venetoclax 1 venetoclax 1 venetoclax 1 rituximab 1 venetoclax 1 venetoclax 1 rituximab 400 mg, n (%) 400 mg, n (%) 600 mg, n (%) 375 mg/m2, n (%) 800 mg, n (%) 600 mg, n (%) 375 mg/m2, n (%) Patients, n 3 6 9 7 4 4 6 39 Injection site reaction 2 (66.7) 6 (100) 6 (66.7) 3 (42.9) 2 (50.0) 2 (50.0) 3 (50.0) 24 (61.5) Diarrhea 0 4 (66.7) 5 (55.6) 3 (42.9) 3 (75.0) 4 (100) 4 (66.7) 23 (59.0) Nausea 1 (33.3) 4 (66.7) 5 (55.6) 3 (42.9) 2 (50.0) 2 (50.0) 1 (16.7) 18 (46.2) Anemia 0 4 (66.7) 4 (44.4) 1 (14.3) 2 (50.0) 3 (75.0) 4 (66.7) 18 (46.2) Thrombocytopenia 0 2 (33.3) 4 (44.4) 2 (28.6) 0 3 (75.0) 2 (33.3) 13 (33.3) Neutropenia 1 (33.3) 1 (16.7) 5 (55.6) 2 (28.6) 0 2 (50.0) 1 (16.7) 12 (30.8) Fatigue 0 2 (33.3) 2 (22.2) 1 (14.3) 2 (50.0) 2 (50.0) 2 (33.3) 11 (28.2) Hypomagnesemia 0 2 (33.3) 2 (22.2) 0 2 (50.0) 2 (50.0) 2 (33.3) 10 (25.6) Decreased appetite 1 (33.3) 1 (16.7) 1 (11.1) 0 2 (50.0) 1 (25.0) 2 (33.3) 8 (20.5) Hypokalemia 0 0 1 (11.1) 1 (14.3) 1 (25.0) 1 (25.0) 3 (50.0) 7 (17.9) Vomiting 0 3 (50.0) 2 (22.2) 0 1 (25.0) 1 (25.0) 0 7 (17.9) Peripheral edema 0 1 (16.7) 2 (22.2) 2 (28.6) 0 0 1 (16.7) 6 (15.4) Pyrexia 0 1 (16.7) 2 (22.2) 1 (14.3) 2 (50.0) 0 0 6 (15.4) Herpes zoster 0 0 2 (22.2) 0 2 (50.0) 1 (25.0) 1 (16.7) 6 (15.4) led to sustained decreases in CD11b during the dosing period. At patients withdrew during cycle 1. Reasons were symptomatic deteri- day 15, the CD11b cell counts were reduced to a median of 42% oration, AEs and clinical progression (2 patients each). For of baseline counts (interquartile range, 34% to 67%) (Figure 2). response information according to cohort, see supplemental Table There was no difference in CD11b reduction according to response 2. The percentage change from baseline of the sum of longest (P 5 .94), but some evidence that the 7 responders with a .50% diameters of the tumor lesions over time is shown in Figure 3. Type reduction in CD11b counts had a longer response (median, 127 and duration of response is shown in Figure 4. Seventy-seven per- days) compared with the 5 responders with a ,50% reduction cent (95% CI, 44-92) of responses lasted for $90 days and 48% (median, 43 days), but this finding is based on very limited data. (95% CI, 4-76) lasted for $180 days. The majority of the 8 com- plete responders (83%) had a duration of response of $90 days. Clinical activity The ORR and CR rate were similar between cell-of-origin (COO) All 39 patients were included in the analysis of clinical activity. subtypes. A high response rate was detected in transformed FL Response assessments by the investigator were available in 33 (ORR, 62%; Table 4). patients. The ORR according to modified Lugano criteria was 38.5%. Complete response was observed in 8 patients (20.5%), Ten of 18 patients (55.6%) for whom the MYC and BCL2 baseline and PR was observed in 7 patients (17.9%). Six patients (15.4%) expression status was known were patients with DE-DLBCL. No had stable disease, and 12 (30.8%) had progressive disease. In 6 patient had double-hit lymphoma. One patient achieved a CR (ie, patients (15.4%) response information was missing as those ORR in DE-DLBCL patients was 10%; Figure 5). Table 3. Treatment-emergent AEs by cohort, grades 3 and 4, in $10% of patients Cohort 1 Cohort 2 Cohort 3 Cohort 3A Cohort 4 Cohort 5 Cohort 5A Total RO 0.45 mg/kg RO RO RO RO 1 Venetoclax RO RO 0.65 mg/kg 0.30 mg/kg 0.45 mg/kg 0.45 mg/kg 600 mg 0.45 mg/kg 0.65 mg/kg 1 Venetoclax 1 Venetoclax 1 Venetoclax 1 Venetoclax 1 Rituximab 1 Venetoclax 1 Venetoclax 600 mg 400 mg, n (%) 400 mg, n (%) 600 mg, n (%) 375 mg/m2, n (%) 800 mg, n (%) 600 mg, n (%) 1 Rituximab 375 mg/m2, n (%) Patients, n 3 6 9 7 4 4 6 39 Neutropenia 1 (33.3) 1 (16.7) 5 (55.6) 1 (14.3) 0 2 (50.0) 1 (16.7) 11 (28.2) Anemia 0 3 (50.0) 1 (11.1) 1 (14.3) 1 (25.0) 2 (50.0) 1 (16.7) 9 (23.1) Thrombocytopenia 0 2 (33.3) 2 (22.2) 2 (28.6) 0 2 (50.0) 1 (16.7) 9 (23.1) Hypokalemia 0 0 0 1 (14.3) 1 (25.0) 0 3 (50.0) 5 (12.8) Febrile Neutropenia 0 1 (16.7) 2 (22.2) 0 0 0 1 (16.7) 4 (10.3) 4766 DICKINSON et al 23 NOVEMBER 2021 • VOLUME 5, NUMBER 22 400 200 CD11b (Percent of baseline count) 100 50 0.30 mg RO, 400 mg Ven 0.45 mg RO, 400 mg Ven 0.45 mg RO, 600 mg Ven 0.45 mg RO, 400 mg Ven + R 25 0.45 mg RO, 800 mg Ven 0.65 mg RO, 600 mg Ven 0.65 mg RO, 600 mg Ven + R Day 1 Day 2 Day 8 Day 15 Figure 2. RO pharmacodynamic profiling as evidence of target engagement. CD11b (molecules of equivalent soluble fluorochrome) change from baseline (%) over time. Ven, venetoclax; R, rituximab. 100 0.30 mg RO, 400 mg Ven 0.45 mg RO, 400 mg Ven 0.45 mg RO, 600 mg Ven 0.45 mg RO, 400 mg Ven + R 0.45 mg RO, 800 mg Ven 50 0.65 mg RO, 600 mg Ven 0.65 mg RO, 600 mg Ven + R Change(%) from baseline 0 —50 —100 0 6 12 18 24 30 36 42 48 Time (Weeks) Figure 3. Sum of longest diameters over time. Percentage change from baseline. Ven, venetoclax; R, rituximab. 23 NOVEMBER 2021 • VOLUME 5, NUMBER 22 PHASE Ib STUDY OF BET INHIBITOR RO6870810 IN DLBCL 4767 0.3 mg RO, 400 mg Ven Assessment/Event 0.45 mg RO, 400 mg Ven CR (complete response) Died PD (progressive disease) PR (partial response) 0.45 mg RO, 600 mg Ven SD (stable disease) Study completion/Early discontinuation Treatment completion/Early discontinuation 0.45 mg RO, 400 mg Ven + R Overall best response CR (complete response) 0.45 mg RO, 800 mg Ven Missing 0.65 mg RO, 600 mg Ven PD (progressive disease) PR (partial response) SD (stable disease) 0.65 mg RO, 600 mg Ven + R 0 21 42 63 84 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 14 27 35 37 10 12 21 23 25 31 42 44 46 48 16 18 29 33 39 Time (days) Figure 4. Swimmers plot according to cohort. Timeline from the first date of treatment to the end of treatment. If the end of treatment was not reached, then the end was last visit, last laboratory assessment, or last AE. Discussion the recommended dose for the triplet regimen, none of the hemato- logic toxicities led to treatment discontinuation. This was enabled by RO1venetoclax1rituximab had a clinically relevant signal of activity treatment interruptions for grade 3 and 4 hematologic events of up that serves as a proof of principle of the rationale driving this trial. to 3 weeks and treatment continuation at lower dose levels if AEs This was a highly refractory population, and some patients enjoyed improved to grade #2. a protracted response to therapy out of keeping with the monother- apy trials of venetoclax or RO. The combination was deliverable, but A lower dose of venetoclax (eg, 400 mg instead of 600 mg), com- with some toxicities that would have to be addressed before further bined with 0.65 mg of RO, may have resulted in a better safety pro- development of the combination. The key toxicities seen in this study file. With a recommended single-agent dose in DLBCL of 1200 mg were largely predictable based on what is known about RO and daily,16 venetoclax doses below 600 mg were not considered to be other BET inhibitors. They are qualitatively similar to those reported efficacious in DLBCL at the time of trial setup. in the FiM trial for RO14 and those known for orally administered bir- Decreases in CD11b in peripheral blood mononuclear cells were abresib18 and molibresib.19 They include fatigue, anemia, and throm- observed with RO treatment, supporting the putative mechanism of bocytopenia, and gastrointestinal side effects, including diarrhea action that RO prevents BET coactivator loading at super- and nausea. The SC administration of RO did not prevent gastroin- enhancers and are indicative of successful target engagement. For testinal toxicities in this study, suggesting that these AEs may repre- sent on-target class effects. CR PR SD PD NE In the FiM trial of RO, grade 3 and 4 anemia and thrombocytopenia occurred in 8.1% and 9.5% of patients, respectively.14 In a phase 1 300 trial of venetoclax in patients with non-Hodgkin lymphoma, grade 3 250 and 4 anemia and thrombocytopenia occurred in 15% and 9% of patients, respectively.16 The higher incidence of these AEs in the 200 MYC (H-Score) trial reported herein indicates an additive effect for the BET inhibi- tor1venetoclax combination, relative to single-agent AE profiles. At 150 Table 4. Response in total population, in transformed FL and by 100 COO subtype GCB ABC Unclassified Total 50 Patients, n 15 5 19 39 0 ORR, n (%) 7 (46.7) 1 (20.0) 7 (36.8) 15 (38.5) 0 100 200 300 CR, n (%) 3 (20.0) 0 5 (26.3) 8 (20.5) BCL2 (H-Score) N-transformed FL Figure 5. Clinical responses according to MYC and BCL2 expression. The Patients, n 3 0 5 8 circled events occurred in patients with DE-DLBCL. SD, stable disease; NE, ORR-transformed FL, n (%) 2 (67.7) 0 3 (60.0) 5 (62.5) not evaluable. 4768 DICKINSON et al 23 NOVEMBER 2021 • VOLUME 5, NUMBER 22 future clinical studies, an assessment beyond cycle 1 and a paired provided editorial assistance supported by funding from F. analysis of tumor tissue with peripheral blood samples may be Hoffmann-La Roche Ltd. instructive about the durability of this effect. This study was sponsored and funded by F. Hoffmann-La Roche Ltd. RO doublet and triplet combinations were active, with responses observed in patients with R/R DLBCL and transformed FL. The ORR of 38.5% and the CR rate of 20.5% across dose and combi- nation cohorts compares favorably to responses observed with RO Authorship and venetoclax administered as a monotherapy. The observation Contribution: M.D., M.D.M., D.R., and M.H. designed the clinical that 48% of responders appear to have a duration of response of study; M.D., J.B., A.F.H., E.G.B., N.G., R.C., S.C.R., and M.H. col- $180 days is an interesting signal in this heavily treated population. lected data; E.N. performed statistical analysis; and all authors ana- By contrast, the FiM trial of RO monotherapy enrolled 13 response- lyzed and interpreted the data and wrote, critically reviewed, and evaluable patients with DLBCL, of whom 2 achieved a PR.14 For approved the manuscript for submission. venetoclax, Davids et al reported an ORR of 18% and a CR rate of 12% in 34 patients with DLBCL, with a median PFS of 1 month.16 Conflict-of-interest disclosure: M.D. reported honoraria from Roche, Amgen, MSD, Janssen, BMS, Novartis; consultancy for Although the overall sample size was small, there is no indication Novartis, Roche, BMS, Gilead, and Janssen; participation on the that clinical activity of the combination treatment was higher in the speakers’ bureau for Novartis; and institutional research funding subgroup of patients with DE-DLBCL. None of the trial patients was from Novartis, Roche, Takeda, Celgene, and MDS. J.B. reported confirmed to have double-hit lymphoma, and further exploration of honoraria from Roche, Takeda, Celgene, Novartis, and Gilead; con- that subgroup is not supported by the efficacy data. sultancy for Takeda, Janssen, Celgene, and Gilead/Kyte; research The high response rate in transformed FL is of interest, but requires funding from Celgene and Roche; and travel grants from Roche, further evaluation in a larger patient sample. Takeda, Celgene, Janssen, and Gilead. A.F.H. reported research funding from BMS, Genentech/Roche, Immune Design, Merck, When the different cohorts were compared, there was no indication Pharmacyclics, and Seattle Genetics; consultancy for Bristol-Myers of a dose-response relationship and no added benefit of rituximab. Squibb, Genentech/Roche, Merck, Seattle Genetics, and Karyo- Treatment duration, as indicated in the swimmers plot (Figure 4), pharm; and travel grants from Bristol-Myers Squibb. E.G.B. reported shows no correlation to dose or added rituximab treatment. The consultancy for Janssen, AbbVie, Celgene, Gilead, Kiowa, EUSA- response rate in the germinal center B-cell and activated B-cell sub- pharma; participation on the speakers’ bureau for Janssen, AbbVie, types appeared to be similar. and Takeda; and travel grants from Janssen, AbbVie, and Roche. Pharmacokinetic analyses confirmed results from the FiM trial and N.G. reported consultancy for Bristol Myers Squibb, TG Therapeu- showed rapid absorption, linearity for exposure across the dose range tics, Seattle Genetics, Janssen, and Pharmacyclics; participation on tested, and a half-life of .10 hour, supporting a once-daily SC the speakers’ bureau for Bristol Myers Squibb, Seattle Genetics, dose.14 Importantly, exposure appears similar to that in previous stud- Janssen, Pharmacyclics, and AbbVie; and research funding from ies, suggesting no impact of venetoclax on RO pharmacokinetics. Bristol Myers Squibb, TG Therapeutics, Pharmacyclics, and Genen- tech. R.C. reports participation on speakers’ bureaus, consultancy, Although the BET inhibitor/venetoclax/rituximab combination and travel funding from Janssen. S.C.R. reported consultancy for resulted in higher response rates compared with that observed AstraZeneca, Celgene, Heron, Juno, Janssen, Karyopharm, Seattle with single agents in patients with heavily pretreated R/R DLBCL, Genetics, Verastem, Dova, and Kite; and research funding from a synergistic effect of that treatment was not shown. Additional Roche/Genentech. E.B., E.L.-T., J.B.-V., B.B., and M.D.M. were studies to understand markers of response and on-treatment phar- employees of Roche during the conduct of the trial. I.F., E.C., K.L., macodynamic effects would be needed to optimize this regimen for broader clinical use, but the priority of such studies seems to E.N., D.R., and M.K. are employees of Roche and own stock. M.H. be low in light of other treatment options, such as anti- reported research funding from and consultancy for Takeda, Roche, CD191lenalidomide, T-cell–engaging bispecific antibodies, anti- and Celgene. body-drug conjugates, and CAR-T cells, which have already been ORCID profiles: M.D., 0000-0002-1492-5966; A.F.H., 0000- shown to provide clinical benefit.20 0002-9665-7415; R.C., 0000-0002-7654-8836; M.H., 0000- 0003-3873-1741. Acknowledgments Correspondence: Michael Dickinson, Clinical Haematology, The authors thank the patients, their families, and the study Peter MacCallum Cancer Centre and Royal Melbourne Hospital, teams at the participating centers. Medical Writers Fiona Russel- Locked Bag 1 A’Beckett St, Melbourne, VIC 8006, Australia; Yarde (FRY Medical Communications Ltd.) and Christian Seitz e-mail: michael.dickinson@petermac.org. References 1. P erez-Salvia M, Esteller M. Bromodomain inhibitors and cancer therapy: from structures to applications. 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