Allogeneic stem cell transplantation for chronic lymphocytic leukemia in the era of novel agents.

Although novel agents (NAs) have improved outcomes for patients with chronic lymphocytic leukemia (CLL), a subset will progress through all available NAs. Understanding outcomes for potentially curative modalities including allogeneic hematopoietic stem cell transplantation (alloHCT) following NA therapy is critical while devising treatment sequences aimed at long-term disease control. In this multicenter, retrospective cohort study, we examined 65 patients with CLL who underwent alloHCT following exposure to ≥1 NA, including baseline disease and transplant characteristics, treatment preceding alloHCT, transplant outcomes, treatment following alloHCT, and survival outcomes. Univariable and multivariable analyses evaluated associations between pre-alloHCT factors and progression-free survival (PFS). Twenty-four-month PFS, overall survival (OS), nonrelapse mortality, and relapse incidence were 63%, 81%, 13%, and 27% among patients transplanted for CLL. Day +100 cumulative incidence of grade III-IV acute graft-vs-host disease (GVHD) was 24%; moderate-severe GVHD developed in 27%. Poor-risk disease characteristics, prior NA exposure, complete vs partial remission, and transplant characteristics were not independently associated with PFS. Hematopoietic cell transplantation-specific comorbidity index independently predicts PFS. PFS and OS were not impacted by having received NAs vs both NAs and chemoimmunotherapy, 1 vs ≥2 NAs, or ibrutinib vs venetoclax as the line of therapy immediately pre-alloHCT. AlloHCT remains a viable long-term disease control strategy that overcomes adverse CLL characteristics. Prior NAs do not appear to impact the safety of alloHCT, and survival outcomes are similar regardless of number of NAs received, prior chemoimmunotherapy exposure, or NA immediately preceding alloHCT. Decisions about proceeding to alloHCT should consider comorbidities and anticipated response to remaining therapeutic options

Safety of Extended Pirtobrutinib Exposure in Relapsed and/or Refractory B-Cell Malignancies.

IntroductionPirtobrutinib, a highly selective, noncovalent (reversible) Bruton tyrosine kinase inhibitor, has demonstrated promising efficacy in B-cell malignancies and is associated with low rates of discontinuation and dose reduction. Pirtobrutinib is administered until disease progression or toxicity, necessitating an understanding of the safety profile in patients with extended treatment.MethodsHere we report the safety of pirtobrutinib in patients with relapsed/refractory B-cell malignancies with extended (≥12 months) drug exposure from the BRUIN trial. Assessments included median time-to-first-occurrence of adverse events (AEs), dose reductions, and discontinuations due to treatment-emergent AEs (TEAEs) and select AEs of interest (AESIs).ResultsOf 773 patients enrolled, 326 (42%) received treatment for ≥12 months. In the extended exposure cohort, the median time-on-treatment was 19 months. The most common all-cause TEAEs were fatigue (32%) and diarrhea (31%). TEAEs leading to dose reduction occurred in 23 (7%) and discontinuations in 11 (3%) extended exposure patients. One patient had a fatal treatment-related AE (COVID-19 pneumonia). Infections (73.0%) were the most common AESI with a median time-to-first-occurrence of 7.4 months. Majority of TEAEs and AESIs occurred during the first year of therapy.ConclusionsPirtobrutinib therapy continues to demonstrate an excellent safety profile amenable to long-term administration without evidence of new or worsening toxicity signals

Tumor Lysis, Adverse Events, and Dose Adjustments in 297 Venetoclax-Treated CLL Patients in Routine Clinical Practice.

PURPOSE: Clinical trials of venetoclax reported negligible rates of clinical tumor lysis syndrome (TLS) in patients with chronic lymphocytic leukemia (CLL) when using an extended dose escalation schedule. We aimed to understand TLS prophylaxis, rates of select adverse events (AE), and impact of dosing modifications in routine clinical practice. EXPERIMENTAL DESIGN: This retrospective cohort study included 297 CLL venetoclax-treated patients outside of clinical trials in academic and community centers. Demographics, baseline disease characteristics, venetoclax dosing, TLS risk and prophylaxis, and AEs were collected. RESULTS: The group was 69% male, 96% had relapsed/refractory CLL, 45% had deletion chromosome 17p, 84% had unmutated IGHV, 80% received venetoclax monotherapy, and median age was 67. TLS risk was categorized as low (40%), intermediate (32%), or high (28%), and 62% had imaging prior to venetoclax initiation. Clinical TLS occurred in 2.7% of patients and laboratory TLS occurred in 5.7%. Pre-venetoclax TLS risk group and creatinine clearance independently predict TLS development in multivariable analysis. Grade 3/4 AEs included neutropenia (39.6%), thrombocytopenia (29.2%), infection (25%), neutropenic fever (7.9%), and diarrhea (6.9%). Twenty-two patients (7.4%) discontinued venetoclax due to an AE. Progression-free survival was similar regardless of number of dose interruptions, length of dose interruption, and stable venetoclax dose. CONCLUSIONS: These data provide insights into current use of venetoclax in clinical practice, including TLS rates observed in clinical practice. We identified opportunities for improved adherence to TLS risk stratification and prophylaxis, which may improve safety

Predictors of SARS-CoV-2 Omicron breakthrough infection after receipt of AZD7442 (tixagevimab-cilgavimab) for pre-exposure prophylaxis among hematologic malignancy patients

AZD7442 (tixagevimab-cilgavimab) is a combination of two human monoclonal antibodies for pre-exposure prophylaxis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection among high-risk patients who do not mount a reliable vaccine response. Foremost among these are hematologic malignancy patients with limited clinical trial or realworld experience to assess the effectiveness of this combination treatment since the emergence of Omicron and its subvariants. We performed a retrospective study of 892 high-risk hematologic malignancy patients who received AZD7442 at Memorial Sloan Kettering Cancer Center in New York City from January 1, 2022 to July 31, 2022. We evaluated demographic, clinical, and laboratory characteristics and performed regression analyses to evaluate risk factors for breakthrough infection. We also evaluated the impact of updated AZD7442 dosing regimens on the risk of breakthrough infection. Among 892 patients, 98 (10.9%) had a breakthrough infection during the study period. A majority received early outpatient treatment (82%) and eventually eight (8.2%) required hospitalization for management of Coronavirus Disease 2019 (COVID-19), with a single instance of severe COVID-19 and death. Patients who received a repeat dose or a higher firsttime dose of AZD7442 had a lower incidence of breakthrough infection. Univariate analyses did not reveal any significant predictors of breakthrough infection. While AZD7442 is effective at reducing SARS-CoV-2 breakthrough infection in patients with hematologic malignancies, no risk factors reliably predicted risk of infection. Patients who received updated dosing regimens as per Food and Drug Administration guidelines had better protection against breakthrough infection

Kinase-Impaired BTK Mutations Are Susceptible to Clinical-Stage BTK and IKZF1/3 Degrader NX-2127

INTRODUCTION: Bruton’s tyrosine kinase (BTK) is a nonreceptor kinase in the B cell receptor (BCR) signaling cascade critical for B cell survival. As such, chronic lymphocytic leukemia (CLL) and other B cell cancers are sensitive to inhibition of BTK. Covalent and noncovalent inhibitors of BTK have revolutionized the treatment of these cancers. Therefore, understanding mechanisms by which acquired mutation in BTK confer drug resistance and developing new therapies to overcome resistance are critically important. RATIONALE: We recently discovered BTK mutations that confer resistance across covalent and noncovalent BTK inhibitors. In this study, we found that a group of these mutants impair BTK kinase activity despite still enabling downstream BCR signaling. We therefore set out to understand the nonenzymatic functions of BTK and explored targeted protein degradation to overcome the oncogenic scaffold function of mutant BTK. This effort included evaluation of BTK degradation in patients with CLL treated in a phase 1 clinical trial of NX-2127, a first-in-class BTK degrader (NCT04830137). RESULTS: BTK enzymatic activity assays revealed that drug resistance mutations in BTK fall into two distinct groups: kinase proficient and kinase impaired. Immunoprecipitation mass spectrometry of kinase-impaired BTK L528W (Leu528→Trp) revealed a scaffold function of BTK with downstream signaling and survival dependent on surrogate kinases that bind to kinase-impaired BTK proteoforms. To target the nonenzymatic functions of BTK, we developed NX-2127, a heterobifunctional molecule that engages the ubiquitin-proteasome system to simultaneously bind both BTK and the cereblon E3 ubiquitin ligase complex, inducing polyubiquitination and proteasome-dependent degradation of IKZF1/3 and all recurrent drug-resistant forms of mutant BTK. The activity of NX-2127 on BTK degradation was further demonstrated in patients with CLL treated in a phase 1 clinical trial of NX-2127, where \u3e80% BTK degradation was achieved and clinical responses were also seen in 79% of evaluable patients, independent of mutant BTK genotypes. CONCLUSION: We identified that BTK inhibitor resistance mutations fall into two distinct functional categories. Kinase-impaired BTK mutants disable BTK kinase activity while promoting physical interactions with other kinases to sustain downstream BCR signaling. This scaffold function of BTK was disrupted by NX-2127, a potent BTK degrader, which showed promising responses for patients with relapsed and refractory CLL, independently of mutant BTK functional category

Mechanisms of Resistance to Noncovalent Bruton's Tyrosine Kinase Inhibitors

BackgroundCovalent (irreversible) Bruton's tyrosine kinase (BTK) inhibitors have transformed the treatment of multiple B-cell cancers, especially chronic lymphocytic leukemia (CLL). However, resistance can arise through multiple mechanisms, including acquired mutations in BTK at residue C481, the binding site of covalent BTK inhibitors. Noncovalent (reversible) BTK inhibitors overcome this mechanism and other sources of resistance, but the mechanisms of resistance to these therapies are currently not well understood.MethodsWe performed genomic analyses of pretreatment specimens as well as specimens obtained at the time of disease progression from patients with CLL who had been treated with the noncovalent BTK inhibitor pirtobrutinib. Structural modeling, BTK-binding assays, and cell-based assays were conducted to study mutations that confer resistance to noncovalent BTK inhibitors.ResultsAmong 55 treated patients, we identified 9 patients with relapsed or refractory CLL and acquired mechanisms of genetic resistance to pirtobrutinib. We found mutations (V416L, A428D, M437R, T474I, and L528W) that were clustered in the kinase domain of BTK and that conferred resistance to both noncovalent BTK inhibitors and certain covalent BTK inhibitors. Mutations in BTK or phospholipase C gamma 2 (PLCγ2), a signaling molecule and downstream substrate of BTK, were found in all 9 patients. Transcriptional activation reflecting B-cell-receptor signaling persisted despite continued therapy with noncovalent BTK inhibitors.ConclusionsResistance to noncovalent BTK inhibitors arose through on-target BTK mutations and downstream PLCγ2 mutations that allowed escape from BTK inhibition. A proportion of these mutations also conferred resistance across clinically approved covalent BTK inhibitors. These data suggested new mechanisms of genomic escape from established covalent and novel noncovalent BTK inhibitors. (Funded by the American Society of Hematology and others.)