Balbas, Minna

Abstract Background: Despite the efficacy of covalent Bruton tyrosine kinase inhibitors (cBTKi) in R/R MCL, patients (pts) ultimately discontinue treatment due to intolerance or development of resistance and disease relapse. Pirtobrutinib is a highly selective, non-covalent BTKi that inhibits BTK with low nM potency throughout the daily dosing interval. Pirtobrutinib was safe and effective in the phase 1/2 BRUIN study in pts with R/R B-cell malignancies, including those previously treated with a BTKi. Pirtobrutinib is approved in the EU for adults with R/R MCL after prior treatment with a BTKi (EMA Conditional Approval, Oct 2023), and in the USA for adults with R/R MCL after ≥ 2 lines of systemic therapy, including a BTKi (FDA Accelerated Approval, Jan 2023).Here, we report the final results from the phase 1/2 BRUIN study (NCT03740529), with a follow-up period of up to 5 yrs, focusing on the efficacy and safety of pirtobrutinib in all R/R MCL pts. Methods: Pts with R/R MCL who received ≥1 prior lines of therapy (including BTKi) were eligible for treatment with pirtobrutinib monotherapy. Key endpoints included overall response rate (ORR), duration of response (DOR) and progression-free survival (PFS), all assessed by independent review committee (IRC) per Lugano 2014 criteria (presented here) and investigator, overall survival (OS), and safety. Pts were included across the range of doses evaluated in dose escalation and expansion (25-300 mg/day). A data cutoff on 27 January 2025 was utilized, with a median study follow-up of 17.5 months (range, 0.5-69.6). Results: Among the 166 pts with R/R MCL, 153 (92%) received the pirtobrutinib approved dose of 200 mg/day, 152 (92%) had received prior cBTKi, of which 128 (84.2%) discontinued any prior cBTKi due to progressive disease (PD), and 15 (9.9%) due to toxicity. The cBTKi-pre-treated pts had a median age of 70 yrs (range, 46-88), 52% had intermediate-risk and 28.3% had high-risk sMIPI scores. The median number of prior lines of therapy was 3 (range 1-9), with most pts having received a prior anti-CD20 antibody (96.7%) and chemotherapy (90.1%). Additional prior therapies included hematopoietic stem cell transplantation (21.7%; 19.7% auto and 4.6% allo), BCL-2 inhibitor (15.8%), CAR-T cell therapy (8.6%). As of the data cutoff, 11 (7.2%) pts who received a prior cBTKi and 6 (42.9%) cBTKi naïve pts remained on treatment. The cBTKi pre-treated pts had an ORR of 49.3% (95% CI, 41.1-57.6), including 15.8% complete responses (CR) (n=24) and 33.6% partial responses (PR) (n=51). The 75 responding pretreated pts had a median DOR of 21.6 months (95% CI, 9.2-27.2) at a median follow-up of 24 months. The ORR among 128 pts who had discontinued any prior cBTKi due to PD and 15 pts who discontinued due to toxicity was 43.0% and 93.3%, respectively. The median PFS and OS for cBTKi pre-treated pts were 5.6 months (95% CI, 5.3-9.2) and 23.9 months (95% CI, 17.3-51.5), respectively. Fourteen pts (9.2%) were censored for PFS due to subsequent anticancer therapy without documented PD, including 8 pts who received CAR-T. The cBTKi naïve pts (n=14) had an ORR of 85.7% (95% CI, 57.2-98.2), including 50.0% CR (n=7) and 35.7% PR (n=5). The 12 responding naïve pts had a median DOR of 42.7 months (95% CI, 25.8-NE) at a median follow-up of 43 months. The median PFS and OS in the cBTKi naïve pts were 44.6 months (95% CI, 16.7-NE) and not reached (95% CI, 33.5-NE), respectively. Among all R/R MCL pts (n=166), the most frequent treatment-emergent adverse events (TEAE), regardless of attribution, were fatigue (31.9%), diarrhea (22.9%), anemia (18.1%), and dyspnea (18.1%). The most common Grade ≥3 TEAE was neutropenia/neutrophil count decreased (13.3%), and the rate of Grade ≥3 infections was 21.1%. Grade ≥3 hemorrhage/hematoma (2.4%) and all-grade atrial fibrillation/flutter (3.6%) were infrequent. In total, 13 (7.8%) pts had a fatal TEAE, with 4 (2.4%) classified as infections. Overall, 8 pts (4.8%) had treatment-related AE leading to dose reductions, and 6 (3.6%) had treatment-related AE leading to pirtobrutinib discontinuation. Conclusion: Pirtobrutinib continues to demonstrate efficacy in pts with heavily pre-treated R/R MCL including both those who previously received a cBTKi and those who were BTKi-naïve. The safety profile of pirtobrutinib remained favorable with a low-rate of dose reductions/discontinuations due to drug-related toxicity. No new safety signals were identified after up to 5 yrs of follow-up.

Background: Despite the efficacy of covalent (c) Bruton tyrosine kinase inhibitors (BTKi) in R/R MCL, disease relapse arises through evolution of resistance mechanisms or development of cBTKi intolerance. Pirtobrutinib, a highly selective, non-covalent (reversible) BTKi has favorable oral pharmacology that enables continuous BTK inhibition throughout the daily dosing interval regardless of the intrinsic rate of BTK turnover. Pirtobrutinib is the first BTKi to demonstrate durable efficacy following prior cBTKi therapy in heavily pre-treated R/R MCL and was well-tolerated with a low frequency of treatment discontinuation due to toxicity (Wang et al., JCO, 2023). Pirtobrutinib is approved in the USA to treat relapsed or refractory MCL after at least two lines of systemic therapy including a prior cBTKi. Here, we report updated results of pirtobrutinib therapy in all patients (pts), including those with biologically high-risk R/R MCL with a median survival follow-up of 24.2 months (range, 18.2-29.8). Methods: Pts with R/R MCL received pirtobrutinib monotherapy in the multicenter Phase 1/2 BRUIN trial (NCT03740529). Efficacy was assessed in all cBTKi pre-treated pts, as well as in cBTKi treatment-naïve pts. Key endpoints included overall response rate (ORR) as assessed by independent review committee per Lugano 2014 criteria, duration of response (DOR), progression-free survival (PFS), overall survival (OS), and safety. Pts were included across the dose escalation range and expansion (25-300 mg/day) with 93% (n=141) receiving at least one dose of 200 mg/day, the FDA-approved dose. A data cut of 05 May 2023 was utilized. Results: Among all 152 pts with R/R MCL who received a prior cBTKi, the median age was 70 years (range, 46-88), and 52% had intermediate-risk and 28.3% had high-risk sMIPI scores. Median prior lines of therapy were 3 (range, 1-9), including an anti-CD20 antibody (96.7%), chemotherapy (90.1%), immunomodulator (17.1%), stem cell transplant (21.7%), BCL-2 inhibitor (15.8%), CAR-T cell therapy (8.6%), and PI3K inhibitor (3.9%). Among pts with high-risk biomarker data available, 30/60 (50%) had TP53 mutations and 45/63 (71%) had a Ki-67 index of ≥30%. The ORR for cBTKi pre-treated pts was 49.3% (95% CI, 41.1-57.6), including 15.8% complete responses (n=24) and 33.6% partial responses (n=51), whilst cBTKi naïve pts (n=14) had an ORR of 85.7% (95% CI, 57.2-98.2). The ORR among 128 pts who had discontinued a prior cBTKi due to PD and 21 pts who had discontinued for toxicity/other reasons was 43.0% and 90.5%, respectively. Among the 75 responding cBTKi pre-treated pts, the median DOR was 21.6 months (95% CI, 9.2-27.2) at a median follow-up of 24 months. The 18- and 24-month DOR rates were 51.9% (95% CI, 37-64.8) and 38.9% (95% CI, 22.7-54.8), respectively. ORR and DOR by high-risk subgroups (including blastoid/pleomorphic variants, Ki-67 index ≥30%, and TP53 mutations) are shown in Table 1. The 18- and 24-month DOR rates among 12 responding cBTKi naïve pts were both 90.0% (95% CI, 47.3-98.5). The median PFS and OS for cBTKi pre-treated pts was 5.6 months (95% CI, 5.3-9.2), and 23.5 months (95% CI, 17.1-NE), respectively. In the MCL cohort (n=166), the most frequent treatment-emergent adverse events (TEAEs) were fatigue (31.9%), diarrhea (22.3%), and dyspnea (17.5%). The most common Grade ≥3 TEAE was neutropenia/neutrophil count decreased (13.3%) and the rate of Grade ≥3 infections was (19.9%). Grade ≥3 hemorrhage/hematoma (2.4%) and all-grade atrial fibrillation/flutter (3.6%) were infrequent. Overall, 8 pts (5%) had treatment-related AEs leading to dose reductions and 5 (3%) had treatment-related AEs leading to pirtobrutinib discontinuation. Conclusion: Pirtobrutinib continues to demonstrate durable efficacy and a favorable safety profile in heavily pre-treated R/R MCL pts with prior cBTKi therapy. High ORRs were observed in pts who had PD on a prior cBTKi, and in pts with high-risk disease features including blastoid/pleomorphic variants, elevated Ki-67 index, and TP53 mutations.

7514 Background: Pirtobrutinib is a highly selective, non-covalent (reversible) BTKi. Here, we report updated results of pirtobrutinib in patients (pts) with cBTKi pre-treated relapsed/refractory (R/R) MCL and more than 3 years follow-up from start of enrollment. Methods: Pts with cBTKi pre-treated R/R MCL received pirtobrutinib monotherapy in a multicenter phase 1/2 BRUIN trial (NCT03740529). Efficacy was assessed in the prespecified primary efficacy cohort that comprised the first 90 enrolled pts who had measurable disease, had received a prior cBTKi, and had no known central nervous system involvement. The primary endpoint was overall response rate (ORR) as assessed by independent review committee. Secondary endpoints included duration of response (DOR) and safety. A data cut of 29 July 2022 was utilized. Results: Among MCL pts who received a prior cBTKi (n=90), median age was 70 years (range, 46-87), median prior lines of therapy were 3 (range, 1-8), 82% discontinued a prior cBTKi due to disease progression, and 78% had intermediate/high risk sMIPI score. Of samples available, 17/36 (47%) had TP53 mutations and 25/34 (74%) had Ki67 ≥30%. The ORR was 57% (95% CI, 46-67), including 19% complete responses (n=17) and 38% partial responses (n=34). At a median follow-up time of 13 months, the median DOR among the 51 responding pts was 17.6 months (95% CI, 7.3-27.2). The 12- and 18-month estimated DOR rates were 58% (95% CI, 41-72) and 45% (95% CI, 27-61), respectively. ORR and DOR by subgroups are shown in the Table. The median progression-free survival was 7.4 months (95% CI, 5.3–13.3). The median overall survival was 23.5 months (95% CI, 15.9-NE). In the MCL safety cohort (n=166), the most frequent treatment-emergent adverse events (TEAE) were fatigue (31%), diarrhea (22%), and anemia (17%). The most common Grade ≥3 TEAE was neutropenia (15%). Grade ≥3 TEAE of hemorrhage (3%) and atrial fibrillation/flutter (2%) were infrequent. Only 5 (3%) pts discontinued due to a treatment-related AE. Conclusions: Pirtobrutinib continues to show durable efficacy and a favorable safety profile in heavily pre-treated R/R MCL pts with prior cBTKi therapy. Responses were observed in pts with high-risk disease features including pts with blastoid/pleomorphic variants, elevated Ki67 index, and TP53 mutations. Clinical trial information: NCT03740529 . [Table: see text]

PURPOSE Pirtobrutinib is a highly selective, noncovalent (reversible) Bruton tyrosine kinase inhibitor (BTKi). We report the safety and efficacy of pirtobrutinib in patients with covalent Bruton tyrosine kinase inhibitor (cBTKi) pretreated mantle-cell lymphoma (MCL), a population with poor prognosis. METHODS Patients with cBTKi pretreated relapsed/refractory (R/R) MCL received pirtobrutinib monotherapy in a multicenter phase I/II trial (BRUIN; ClinicalTrials.gov identifier: NCT03740529 ). Efficacy was assessed in the first 90 consecutively enrolled patients who met criteria for inclusion in the primary efficacy cohort. The primary end point was overall response rate (ORR). Secondary end points included duration of response (DOR) and safety. RESULTS The median patient age was 70 years (range, 46-87), the median prior lines of therapy was 3 (range, 1-8), 82.2% had discontinued a prior cBTKi because of disease progression, and 77.8% had intermediate- or high-risk simplified MCL International Prognostic Index score. The ORR was 57.8% (95% CI, 46.9 to 68.1), including 20.0% complete responses (n = 18). At a median follow-up of 12 months, the median DOR was 21.6 months (95% CI, 7.5 to not reached). The 6- and 12-month estimated DOR rates were 73.6% and 57.1%, respectively. In the MCL safety cohort (n = 164), the most common treatment-emergent adverse events (TEAEs) were fatigue (29.9%), diarrhea (21.3%), and dyspnea (16.5%). Grade ≥3 TEAEs of hemorrhage (3.7%) and atrial fibrillation/flutter (1.2%) were less common. Only 3% of patients discontinued pirtobrutinib because of a treatment-related adverse event. CONCLUSION Pirtobrutinib is a first-in-class novel noncovalent (reversible) BTKi and the first BTKi of any kind to demonstrate durable efficacy after prior cBTKi therapy in heavily pretreated R/R MCL. Pirtobrutinib was well tolerated with low rates of treatment discontinuation because of toxicity.

Abstract Background: Covalent Bruton's Tyrosine Kinase (BTK) inhibitors (BTKi) have transformed the management of relapsed mantle cell lymphoma (MCL), but these treatments are not curative and the majority of patients will require additional treatment. Covalent BTKi share pharmacologic liabilities (e.g. low oral bioavailability, short half-life) that collectively may lead to suboptimal BTK target coverage especially in rapidly proliferating tumors with high BTK protein turnover such as MCL. To address these limitations, pirtobrutinib, a highly selective, non-covalent BTKi that inhibits both wild type (WT) and C481-mutated BTK with equal low nM potency was developed. In the phase 1/2 BRUIN study, pirtobrutinib achieved pharmacokinetic exposures that exceeded its BTK IC96 at trough, was well tolerated, and demonstrated promising efficacy in heavily pretreated, poor-prognosis MCL patients, most of whom had prior treatment with a covalent BTKi (Mato et al. Lancet 2021;397,10277:892-901). The purpose of this randomized study is to demonstrate the superiority of pirtobrutinib compared to investigator's choice of covalent BTKi in patients with previously treated MCL. Study Design and Methods: BRUIN MCL-321 is a randomized, open-label, global phase 3 study comparing pirtobrutinib monotherapy versus investigator's choice of covalent BTKi monotherapy (ibrutinib, acalabrutinib, or zanubrutinib) in patients with previously treated, BTKi naïve MCL. Approximately 500 patients will be randomized 1:1. Randomization will be stratified by sMIPI risk (low/intermediate vs high), comparator BTKi (ibrutinib vs acalabrutinib/ zanubrutinib), and number of prior lines of therapy (1 vs ≥ 2). Eligible patients are adults aged ≥18 years with a confirmed diagnosis of MCL (cyclin D1 overexpression, and ≥ 1 B-cell marker) who have received ≥ 1 prior line of systemic therapy for MCL that did not include a prior BTKi. Patients must have measurable disease per Lugano criteria and must have progressed on or relapsed following the most recent line of therapy prior to study enrollment. Key exclusion criteria include a history of current or prior CNS involvement, significant cardiovascular disease, stroke, or intracranial hemorrhage within 6 months of randomization, and allogeneic stem cell transplant (SCT), autologous SCT or chimeric antigen receptor (CAR) T-cell therapy within 60 days of randomization. The primary endpoint is progression-free survival (PFS) per Lugano criteria assessed by an independent review committee (IRC), with the goal of demonstrating superiority of pirtobrutinib over investigator's choice of covalent BTKi. Secondary endpoints include overall response rate (ORR), duration of response (DoR), investigator-assessed PFS per Lugano criteria, overall survival (OS), event-free survival (EFS), time to treatment failure (TTF), time to next treatment (TTNT), time from randomization to disease progression on next line of treatment or death from any cause (PFS2), safety and tolerability, and patient reported outcomes. This global study is currently enrolling patients (NCT04662255). Disclosures Eyre: Gilead/KITE: Honoraria, Other: Travel support for conferences, Research Funding, Speakers Bureau; Janssen: Honoraria; Loxo Oncology: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Consultancy; Abbvie: Consultancy, Honoraria, Other: Travel to conferences; Roche: Consultancy, Honoraria; AstraZeneca: Honoraria, Research Funding; Beigene: Honoraria, Research Funding; Secura Bio: Consultancy, Honoraria. Shah: Miltenyi Biotec: Consultancy, Honoraria, Research Funding; Kite: Consultancy; Epizyme: Consultancy; Umoja: Consultancy; Legend: Consultancy; Incyte: Consultancy; Lily: Consultancy, Honoraria, Research Funding. Dreyling: Novartis: Consultancy, Speakers Bureau; Janssen: Consultancy, Research Funding, Speakers Bureau; Roche: Consultancy, Research Funding, Speakers Bureau; Astra Zeneca: Consultancy, Speakers Bureau; BeiGene: Consultancy; Celgene: Consultancy, Research Funding, Speakers Bureau; Amgen: Speakers Bureau; Genmab: Consultancy; Bayer HealthCare Pharmaceuticals: Consultancy, Research Funding, Speakers Bureau; Gilead/Kite: Consultancy, Research Funding, Speakers Bureau; Abbvie: Research Funding; Incyte: Consultancy, Speakers Bureau. Vandenberghe: Jansnens: Honoraria; Abbvie: Honoraria. Jurczak: Abbvie, AstraZeneca, BeiGene, Celtrion, Celgene, Debbiopharm, Epizyme, Incyte, Janssen, Loxo Oncology, Merck, Mei Pharma, Morphosys, Novo Nordisk, Roche, Sandoz, Takeda, TG Therapeutics: Research Funding; Astra Zeneca, BeiGene, Janssen, Loxo Oncology, Sandoz, Roche,: Membership on an entity's Board of Directors or advisory committees. Wang: Genentech: Research Funding; Eli Lilly: Membership on an entity's Board of Directors or advisory committees; MorphoSys: Research Funding; LOXO Oncology: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Research Funding; InnoCare: Research Funding; Incyte: Membership on an entity's Board of Directors or advisory committees, Research Funding; TG Therapeutics: Membership on an entity's Board of Directors or advisory committees. Cheah: Loxo/Lilly: Consultancy, Honoraria, Other: advisory; Janssen: Consultancy, Honoraria, Other: advisory; Roche: Consultancy, Honoraria, Other: advisory and travel expenses, Research Funding; TG Therapeutics: Consultancy, Honoraria, Other: advisory; AstraZeneca: Consultancy, Honoraria, Other: advisory; Celgene: Research Funding; AbbVie: Research Funding; Beigene: Consultancy, Honoraria, Other: advisory; Ascentage pharma: Consultancy, Honoraria, Other: advisory; Gilead: Consultancy, Honoraria, Other: advisory; MSD: Consultancy, Honoraria, Other: advisory, Research Funding. Gandhi: Karyopharm Therapeutics: Honoraria; TG Therapeutics: Honoraria; GlaxoSmithKline: Honoraria. Sharman: AstraZeneca: Consultancy; Lilly: Consultancy; Pharmacyclics LLC, an AbbVie Company: Consultancy; Centessa: Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees; BeiGene: Consultancy; BMS: Consultancy; TG Therapeutics: Consultancy; AbbVie: Consultancy. Andorsky: Abbvie: Consultancy, Research Funding; Celgene/BMS: Consultancy, Research Funding; Epizyme: Research Funding. Yin: Loxo Oncology at Lilly: Current Employment; AstraZeneca: Ended employment in the past 24 months. Balbas: Nektar Therapeutics: Current equity holder in publicly-traded company, Ended employment in the past 24 months; Loxo Oncology at Lilly: Current Employment, Current equity holder in publicly-traded company. Kherani: Loxo Oncology at Lilly: Current Employment, Current equity holder in publicly-traded company. Wang: AstraZeneca, Bayer Healthcare, BeiGene, CSTone, DTRM Biopharma (Cayman) Limited, Epizyme, Genentech, InnoCare, Janssen, Juno, Kite Pharma, Loxo Oncology, Miltenyi Biomedicine GmbH, Oncternal, Pharmacyclics, VelosBio: Consultancy; Acerta Pharma, AstraZeneca, BeiGene, BioInvent, Celgene, Innocare, Janssen, Juno, Kite, Pharma, Lilly, Loxo Oncology, Molecular Templates, Oncternal, Pharmacyclics, VelosBio: Research Funding; Acerta Pharma, Anticancer Association, AstraZeneca, BeiGene, CAHON, Chinese Medical Association, Clinical Care Options, Dava Oncology, Epizyme, Hebei Cancer Prevention Federation, Imbruvica, Imedex, Janssen, Kite Pharma, Miltenyi Biomedicine GmbH, Moffit : Honoraria.