Neutrophil elastase as a versatile cleavage enzyme for activation of αvß3 integrin-targeted small molecule drug conjugates with different payload classes in the tumor microenvironment.

Introduction: The development of bioconjugates for the targeted delivery of anticancer agents is gaining momentum after recent success of antibody drug conjugates (ADCs) in the clinic. Smaller format conjugates may have several advantages including better tumor penetration; however, cellular uptake and trafficking may be substantially different from ADCs. To fully leverage the potential of small molecule drug conjugates (SMDCs) with potent binding molecules mediating tumor homing, novel linker chemistries susceptible for efficient extracellular activation and payload release in the tumor microenvironment (TME) need to be explored. Methods: We designed a novel class of SMDCs, which target αvß3 integrins for tumor homing and are cleaved by neutrophil elastase (NE), a serine protease active in the TME. A peptidomimetic αvß3 ligand was attached via optimized linkers composed of substrate peptide sequences of NE connected to different functional groups of various payload classes, such as camptothecins, monomethyl auristatin E, kinesin spindle protein inhibitors (KSPi) and cyclin-dependent kinase 9 inhibitors (CDK-9i). Results: NE-mediated cleavage was found compatible with the diverse linker attachments via hindered ester bonds, amide bonds and sulfoximide bonds. Efficient and traceless release of the respective payloads was demonstrated in biochemical assays. The newly designed SMDCs were highly stable in buffer as well as in rat and human plasma. Cytotoxicity of the SMDCs in cancer cell lines was clearly dependent on NE. IC50 values were in the nanomolar or sub-nanomolar range across several cancer cell lines reaching similar potencies as compared to the respective payloads only in the presence of NE. In vivo pharmacokinetics evaluating SMDC and free payload exposures in rat and particularly the robust efficacy with good tolerability in triple negative breast and small cell lung cancer murine models demonstrate the utility of this approach for selective delivery of payloads to the tumor. Discussion: These results highlight the broad scope of potential payloads and suitable conjugation chemistries paving the way for future SMDCs harnessing the safety features of targeted delivery approaches in combination with NE cleavage in the TME.

Enitociclib, a Selective CDK9 Inhibitor, Induces Complete Regression of MYC+ Lymphoma by Downregulation of RNA Polymerase II Mediated Transcription.

Double-hit diffuse large B-cell lymphoma (DH-DLBCL) is an aggressive, and often refractory, type of B-cell non-Hodgkin lymphoma (NHL) characterized by rearrangements in MYC and BCL2. Cyclin-dependent kinase 9 (CDK9) regulates transcriptional elongation and activation of transcription factors, including MYC, making it a potential targeted approach for the treatment of MYC+ lymphomas. Enitociclib is a well-tolerated and clinically active CDK9 inhibitor leading to complete metabolic remissions in 2 of 7 patients with DH-DLBCL treated with once weekly 30 mg intravenous administration. Herein, we investigate the pharmacodynamic effect of CDK9 inhibition in preclinical models and in blood samples from patients [DH-DLBCL (n = 10) and MYC+ NHL (n = 5)] treated with 30 mg i.v. once weekly enitociclib. Enitociclib shows significant regulation of RNA polymerase II Ser2 phosphorylation in a MYC-amplified SU-DHL-4 cell line and depletion of MYC and antiapoptosis protein MCL1 in SU-DHL-4 and MYC-overexpressing SU-DHL-10 cell lines in vitro. Tumor growth inhibition reaching 0.5% of control treated SU-DHL-10 xenografts is achieved in vivo and MYC and MCL1 depletion as well as evidence of apoptosis activation after enitociclib treatment is demonstrated. An unbiased analysis of the genes affected by CDK9 inhibition in both cell lines demonstrates that RNA polymerase II and transcription pathways are primarily affected and novel enitociclib targets such as PHF23 and TP53RK are discovered. These findings are recapitulated in blood samples from enitociclib-treated patients; while MYC downregulation is most robust with enitociclib treatment, other CDK9-regulated targets may be MYC independent delivering a transcriptional downregulation via RNA polymerase II. SIGNIFICANCE: MYC+ lymphomas are refractory to standard of care and novel treatments that downregulate MYC are needed. The utility of enitociclib, a selective CDK9 inhibitor in this patient population, is demonstrated in preclinical models and patients. Enitociclib inhibits RNA polymerase II function conferring a transcriptional shift and depletion of MYC and MCL1. Enitociclib intermittent dosing downregulates transcription factors including MYC, providing a therapeutic window for durable responses in patients with MYC+ lymphoma.

Discovery of VIP236, an αvß3-Targeted Small-Molecule-Drug Conjugate with Neutrophil Elastase-Mediated Activation of 7-Ethyl Camptothecin Payload for Treatment of Solid Tumors.

The emerging field of small-molecule-drug conjugates (SMDCs) using small-molecule biomarker-targeted compounds for tumor homing may provide new perspectives for targeted delivery. Here, for the first time, we disclose the structure and the synthesis of VIP236, an SMDC designed for the treatment of metastatic solid tumors by targeting αvß3 integrins and extracellular cleavage of the 7-ethyl camptothecin payload by neutrophil elastase in the tumor microenvironment. Imaging studies in the Lewis lung mouse model using an elastase cleavable quenched substrate showed pronounced elastase activity in the tumor. Pharmacokinetics studies of VIP236 in tumor-bearing mice demonstrated high stability of the SMDC in plasma and high tumor accumulation of the cleaved payload. Studies in bile-duct-cannulated rats showed that biliary excretion of the unmodified conjugate is the primary route of elimination. Treatment- and time-dependent phosphorylation of H2AX, a marker of DNA damage downstream of topoisomerase 1 inhibition, verified the on-target activity of the payload cleaved from VIP236 in vivo. Treatment with VIP236 resulted in long-lasting tumor regression in subcutaneous patient-derived xenograft (PDX) models from patients with non-small-cell lung, colon, and renal cancer as well as in two orthotopic metastatic triple-negative breast cancer PDX models. In these models, a significant reduction of brain and lung metastases also was observed.

VIP152 is a selective CDK9 inhibitor with pre-clinical in vitro and in vivo efficacy in chronic lymphocytic leukemia.

Chronic lymphocytic leukemia (CLL) is effectively treated with targeted therapies including Bruton tyrosine kinase inhibitors and BCL2 antagonists. When these become ineffective, treatment options are limited. Positive transcription elongation factor complex (P-TEFb), a heterodimeric protein complex composed of cyclin dependent kinase 9 (CDK9) and cyclin T1, functions to regulate short half-life transcripts by phosphorylation of RNA Polymerase II (POLII). These transcripts are frequently dysregulated in hematologic malignancies; however, therapies targeting inhibition of P-TEFb have not yet achieved approval for cancer treatment. VIP152 kinome profiling revealed CDK9 as the main enzyme inhibited at 100 nM, with over a 10-fold increase in potency compared with other inhibitors currently in development for this target. VIP152 induced cell death in CLL cell lines and primary patient samples. Transcriptome analysis revealed inhibition of RNA degradation through the AU-Rich Element (ARE) dysregulation. Mechanistically, VIP152 inhibits the assembly of P-TEFb onto the transcription machinery and disturbs binding partners. Finally, immune competent mice engrafted with CLL-like cells of Eµ-MTCP1 over-expressing mice and treated with VIP152 demonstrated reduced disease burden and improvement in overall survival compared to vehicle-treated mice. These data suggest that VIP152 is a highly selective inhibitor of CDK9 that represents an attractive new therapy for CLL.

A Small Molecule-Drug Conjugate (SMDC) Consisting of a Modified Camptothecin Payload Linked to an αVß3 Binder for the Treatment of Multiple Cancer Types.

To improve tumor selectivity of cytotoxic agents, we designed VIP236, a small molecule-drug conjugate consisting of an αVß3 integrin binder linked to a modified camptothecin payload (VIP126), which is released by the enzyme neutrophil elastase (NE) in the tumor microenvironment (TME). The tumor targeting and pharmacokinetics of VIP236 were studied in tumor-bearing mice by in vivo near-infrared imaging and by analyzing tumor and plasma samples. The efficacy of VIP236 was investigated in a panel of cancer cell lines in vitro, and in MX-1, NCI-H69, and SW480 murine xenograft models. Imaging studies with the αVß3 binder demonstrated efficient tumor targeting. Administration of VIP126 via VIP236 resulted in a 10-fold improvement in the tumor/plasma ratio of VIP126 compared with VIP126 administered alone. Unlike SN38, VIP126 is not a substrate of P-gp and BCRP drug transporters. VIP236 presented strong cytotoxic activity in the presence of NE. VIP236 treatment resulted in tumor regressions and very good tolerability in all in vivo models tested. VIP236 represents a novel approach for delivering a potent cytotoxic agent by utilizing αVß3 as a targeting moiety and NE in the TME to release the VIP126 payload-designed for high permeability and low efflux-directly into the tumor stroma.

First-in-Human Dose-Escalation Study of Cyclin-Dependent Kinase 9 Inhibitor VIP152 in Patients with Advanced Malignancies Shows Early Signs of Clinical Efficacy.

PURPOSE: To report on the first-in-human phase I study of VIP152 (NCT02635672), a potent and highly selective cyclin-dependent kinase 9 (CDK9) inhibitor. PATIENTS AND METHODS: Adults with solid tumors or aggressive non-Hodgkin lymphoma who were refractory to or had exhausted all available therapies received VIP152 monotherapy as a 30-minute intravenous, once-weekly infusion, as escalating doses (5, 10, 15, 22.5, or 30 mg in 21-day cycles) until the MTD was determined. RESULTS: Thirty-seven patients received ≥ 1 VIP152 dose, with 30 mg identified as the MTD based on dose-limiting toxicity of grade 3/4 neutropenia. The most common adverse events were nausea and vomiting (75.7% and 56.8%, respectively), all of grade 1/2 severity. Of the most common events, grade 3/4 events occurring in > 1 patient were neutropenia (22%), anemia (11%), abdominal pain (8%), increased alkaline phosphatase (8%), and hyponatremia (8%). Day 1 exposure for the MTD exceeded the predicted minimum therapeutic exposure and reproducibly achieved maximal pathway modulation; no accumulation occurred after multiple doses. Seven of 30 patients with solid tumors had stable disease (including 9.5 and 16.8 months in individual patients with pancreatic cancer and salivary gland cancer, respectively), and 2 of 7 patients with high-grade B-cell lymphoma with MYC and BCL2/BCL6 translocations (HGL) achieved durable complete metabolic remission (ongoing at study discontinuation, after 3.7 and 2.3 years of treatment). CONCLUSIONS: VIP152 monotherapy, administered intravenously once weekly, demonstrated a favorable safety profile and evidence of clinical benefit in patients with advanced HGL and solid tumors.

Evaluation of the Pharmacokinetics and Safety of a Single Dose of Acalabrutinib in Subjects With Hepatic Impairment.

Acalabrutinib received approval for the treatment of adult patients with mantle cell lymphoma who received at least 1 prior therapy and adult patients with chronic lymphocytic leukemia or small lymphocytic lymphoma. This study investigated the impact of hepatic impairment (HI) on acalabrutinib pharmacokinetics (PK) and safety at a single 50-mg dose in fasted subjects. This study was divided into 2 parts: study 1, an open-label, parallel-group study in Child-Pugh class A or B subjects and healthy subjects; and study 2, an open-label, parallel-group study in Child-Pugh class C subjects and healthy subjects. Baseline characteristics and safety profiles were similar across groups. Acalabrutinib exposure (area under the plasma concentration-time curve) increased slightly (1.90- and 1.48-fold) in subjects with mild (Child-Pugh class A) and moderate (Child-Pugh class B) hepatic impairment compared with healthy subjects. In severe hepatic impairment (Child-Pugh class C), acalabrutinib exposure (area under the plasma concentration-time curve and maximum plasma concentration) increased ≈5.0- and 3.6-fold, respectively. Results were consistent across total and unbound exposures. Severe hepatic impairment did not impact total/unbound metabolite (ACP-5862) exposures; the metabolite-to-parent ratio decreased to 0.6 to 0.8 (vs 3.1-3.6 in healthy subjects). In summary, single oral dose of 50-mg acalabrutinib was safe and well tolerated in subjects with mild, moderate, and severe hepatic impairment and in healthy control subjects. In subjects with severe hepatic impairment, mean acalabrutinib exposure increased by up to 5-fold and should be avoided. Acalabrutinib does not require dose adjustment in patients with mild or moderate hepatic impairment.

Acalabrutinib monotherapy for treatment of chronic lymphocytic leukaemia (ACE-CL-001): analysis of the Richter transformation cohort of an open-label, single-arm, phase 1-2 study.

BACKGROUND: Patients with chronic lymphocytic leukaemia who progress to Richter transformation (diffuse large B-cell lymphoma morphology) have few therapeutic options. We analysed data from the Richter transformation cohort of a larger, ongoing, phase 1-2, single-arm study evaluating the safety and activity of the selective, irreversible Bruton's tyrosine kinase inhibitor acalabrutinib for the treatment of chronic lymphocytic leukaemia or small lymphocytic lymphoma. METHODS: For this open-label, single-arm, phase 1-2 study, patients aged 18 years or older with biopsy-proven treatment-naive or previously treated diffuse large B-cell lymphoma (Richter transformation) or prolymphocytic leukaemia transformation (Eastern Cooperative Oncology Group performance status ≤2) were assigned to receive oral acalabrutinib 200 mg twice daily as monotherapy until disease progression or toxicity. Patients were enrolled across seven centres from four countries. Safety and pharmacokinetics were assessed as primary endpoints; secondary endpoints were overall response rate, duration of response, and progression-free survival. Safety was assessed in the all-treated population (patients who received ≥1 dose), and activity was assessed in the all-treated population (for progression-free survival) and efficacy-evaluable population (for response rate; patients in the all-treated population with ≥1 response assessment after the first dose). This trial is registered with ClinicalTrials.gov (NCT02029443). FINDINGS: Between Sept 2, 2014, and April 25, 2016, 25 patients with Richter transformation were enrolled; 12 (48%) were male and 23 (92%) were White. As of data cutoff (March 1, 2021), two (8%) of 25 patients remained on acalabrutinib. The median time on study was 2·6 months (IQR 1·8-8·4). The most common adverse events (all grades) were diarrhoea (12 [48%] of 25 patients), headache (11 [44%]), and anaemia (eight [32%]). The most common grade 3-4 adverse events were neutropenia (seven [28%] of 25) and anaemia (five [20%]). The most common reason for treatment discontinuation was disease progression (17 [68%] of 25 patients). 11 (44%) deaths were reported within 30 days of the last acalabrutinib dose; none was considered treatment-related. Acalabrutinib was rapidly absorbed and eliminated, with similar day 1 and day 8 exposures. The overall response rate was 40·0% (95% CI 21·1-61·3), with two (8%) of 25 patients having a complete response and eight (32%) having a partial response; the median duration of response was 6·2 months (95% CI 0·3-14·8). Median progression-free survival in the overall cohort was 3·2 months (95% CI 1·8-4·0). INTERPRETATION: Acalabrutinib appears to be generally well tolerated, although progression-free survival was relatively poor in this cohort of patients with Richter transformation. On the basis of these findings, the use of acalabrutinib monotherapy in this setting is limited; however, further assessment of acalabrutinib as part of combination-based regimens for patients with Richter transformation is warranted. FUNDING: Acerta Pharma, a member of the AstraZeneca Group.

Changing for the Better: Discovery of the Highly Potent and Selective CDK9 Inhibitor VIP152 Suitable for Once Weekly Intravenous Dosing for the Treatment of Cancer.

Selective inhibition of exclusively transcription-regulating positive transcription elongation factor b/CDK9 is a promising new approach in cancer therapy. Starting from atuveciclib, the first selective CDK9 inhibitor to enter clinical development, lead optimization efforts aimed at identifying intravenously (iv) applicable CDK9 inhibitors with an improved therapeutic index led to the discovery of the highly potent and selective clinical candidate VIP152. The evaluation of various scaffold hops was instrumental in the identification of VIP152, which is characterized by the underexplored benzyl sulfoximine group. VIP152 exhibited the best preclinical overall profile in vitro and in vivo, including high efficacy and good tolerability in xenograft models in mice and rats upon once weekly iv administration. VIP152 has entered clinical trials for the treatment of cancer with promising longterm, durable monotherapy activity in double-hit diffuse large B-cell lymphoma patients.

A phase 1/2 study of the combination of acalabrutinib and vistusertib in patients with relapsed/refractory B-cell malignancies.

In a phase 1b study of acalabrutinib (a covalent Bruton tyrosine kinase (BTK) inhibitor) in combination with vistusertib (a dual mTORC1/2 inhibitor) in patients with relapsed/refractory diffuse large B-cell lymphoma (DLBCL), multiple ascending doses of the combination as intermittent or continuous schedules of vistusertib were evaluated. The overall response rate was 12% (3/25). The pharmacodynamic (PD) profile for acalabrutinib showed that BTK occupancy in all patients was >95%. In contrast, PD analysis for vistusertib showed variable inhibition of phosphorylated 4EBP1 (p4EBP1) without modulation of AKT phosphorylation (pAKT). The pharmacokinetic (PK)/PD relationship of vistusertib was direct for TORC1 inhibition (p4EBP1) but did not correlate with TORC2 inhibition (pAKT). Cell-of-origin subtyping or next-generation sequencing did not identify a subset of DLBCL patients with clinical benefit; however, circulating tumor DNA dynamics correlated with radiographic response. These data suggest that vistusertib does not modulate targets sufficiently to add to the clinical activity of acalabrutinib monotherapy. Clinicaltrials.gov identifier: NCT03205046.

Acalabrutinib Versus Ibrutinib in Previously Treated Chronic Lymphocytic Leukemia: Results of the First Randomized Phase III Trial.

PURPOSE: Among Bruton's tyrosine kinase inhibitors, acalabrutinib has greater selectivity than ibrutinib, which we hypothesized would improve continuous therapy tolerability. We conducted an open-label, randomized, noninferiority, phase III trial comparing acalabrutinib and ibrutinib in patients with chronic lymphocytic leukemia (CLL). METHODS: Patients with previously treated CLL with centrally confirmed del(17)(p13.1) or del(11)(q22.3) were randomly assigned to oral acalabrutinib 100 mg twice daily or ibrutinib 420 mg once daily until progression or unacceptable toxicity. The primary end point was independent review committee-assessed noninferiority of progression-free survival (PFS). RESULTS: Overall, 533 patients (acalabrutinib, n = 268; ibrutinib, n = 265) were randomly assigned. At the data cutoff, 124 (46.3%) acalabrutinib patients and 109 (41.1%) ibrutinib patients remained on treatment. After a median follow-up of 40.9 months, acalabrutinib was determined to be noninferior to ibrutinib with a median PFS of 38.4 months in both arms (95% CI acalabrutinib, 33.0 to 38.6 and ibrutinib, 33.0 to 41.6; hazard ratio: 1.00; 95% CI, 0.79 to 1.27). All-grade atrial fibrillation/atrial flutter incidence was significantly lower with acalabrutinib versus ibrutinib (9.4% v 16.0%; P = .02); among other selected secondary end points, grade 3 or higher infections (30.8% v 30.0%) and Richter transformations (3.8% v 4.9%) were comparable between groups and median overall survival was not reached in either arm (hazard ratio, 0.82; 95% CI, 0.59 to 1.15), with 63 (23.5%) deaths with acalabrutinib and 73 (27.5%) with ibrutinib. Treatment discontinuations because of adverse events occurred in 14.7% of acalabrutinib-treated patients and 21.3% of ibrutinib-treated patients. CONCLUSION: In this first direct comparison of less versus more selective Bruton's tyrosine kinase inhibitors in CLL, acalabrutinib demonstrated noninferior PFS with fewer cardiovascular adverse events.

Pooled analysis of safety data from clinical trials evaluating acalabrutinib monotherapy in mature B-cell malignancies.

Bruton tyrosine kinase (BTK) inhibition is an effective therapy for many B-cell malignancies. Acalabrutinib is a next-generation, potent, highly selective, covalent BTK inhibitor. To characterize acalabrutinib tolerability, we pooled safety data from 1040 patients with mature B-cell malignancies treated with acalabrutinib monotherapy in nine clinical studies (treatment-naïve: n = 366 [35%], relapsed/refractory: n = 674 [65%]; median [range] age: 67 [32-90] years; median [range] prior treatments: 1 [0-13]; median [range] duration of exposure: 24.6 [0.0-58.5] months). The most common adverse events (AEs) were headache (38%), diarrhea (37%), upper respiratory tract infection (22%), contusion (22%), nausea (22%), fatigue (21%), and cough (21%). Serious AEs (SAEs) occurred in 39% of patients; pneumonia (6%) was the only SAE that occurred in ≥2%. Deaths due to AEs occurred in 52 patients (5%); pneumonia (n = 8) was the only fatal AE to occur in ≥3 patients. AEs led to treatment discontinuation in 9%. Rates for the AEs of interest (all grades) included infections (67%), hemorrhages (46%), neutropenia (16%), anemia (14%), second primary malignancies (12%), thrombocytopenia (9%), hypertension (8%), and atrial fibrillation (4%). This pooled analysis confirmed acalabrutinib's tolerability and identified no newly emerging late toxicities, supporting acalabrutinib as a long-term treatment for patients with mature B-cell malignancies.

Phase II study of acalabrutinib in ibrutinib-intolerant patients with relapsed/refractory chronic lymphocytic leukemia.

B-cell receptor signalling inhibition by targeting Bruton tyrosine kinase (BTK) is effective in treating chronic lymphocytic leukemia (CLL). The BTK inhibitor ibrutinib may be intolerable for some patients. Acalabrutinib is a more selective BTK inhibitor that may be better tolerated by patients who are intolerant to ibrutinib. A phase 2 study of acalabrutinib was conducted in patients with relapsed/refractory CLL who were ibrutinib-intolerant and had continued disease activity. Intolerance was defined as having discontinued ibrutinib due to persistent grade 3/4 adverse events (AEs) or persistent/recurrent grade 2 AEs despite dose modification/interruption. Patients received oral acalabrutinib 100 mg twice daily until disease progression or intolerance. Sixty patients were treated. Overall response rate to acalabrutinib was 73% and three patients (5%) achieved complete remission. At median follow-up of 35 months, the median progressionfree and overall survival were not reached; 24-month estimates were 72% and 81%, respectively. The most frequent AEs with acalabrutinib were diarrhea (53%), headache (42%), contusion (40%), dizziness (33%), upper respiratory tract infection (33%), and cough (30%). Most common reasons for acalabrutinib discontinuation were progressive disease (23%) and AEs (17%). Most patients with baseline samples (49/52; 94%) and all with on-treatment samples (3/3; 100%) had no detectable BTK and/or PLCG2 mutations. Acalabrutinib is effective and tolerable in most patients with relapsed/refractory CLL who are intolerant of ibrutinib. Acalabrutinib may be useful for patients who may benefit from BTK inhibitor therapy but are ibrutinib intolerant.

Acalabrutinib in treatment-naive chronic lymphocytic leukemia.

Acalabrutinib has demonstrated significant efficacy and safety in relapsed chronic lymphocytic leukemia (CLL). Efficacy and safety of acalabrutinib monotherapy were evaluated in a treatment-naive CLL cohort of a single-arm phase 1/2 trial (ACE-CL-001). Adults were eligible for enrollment if chemotherapy was declined or deemed inappropriate due to comorbidities (N = 99). Patients had a median age of 64 years and 47% had Rai stage III/IV disease. Acalabrutinib was administered orally 200 mg once daily, or 100 mg twice daily until progression or intolerance. A total of 99 patients were treated; 57 (62%) had unmutated immunoglobulin heavy-chain variable gene, and 12 (18%) had TP53 aberrations. After median follow-up of 53 months, 85 patients remain on treatment; 14 discontinued treatment, mostly because of adverse events (AEs) (n = 6) or disease progression (n = 3). Overall response rate was 97% (90% partial response; 7% complete response), with similar outcomes among all prognostic subgroups. Because of improved trough BTK occupancy with twice-daily dosing, all patients were transitioned to 100 mg twice daily. Median duration of response (DOR) was not reached; 48-month DOR rate was 97% (95% confidence interval, 90-99). Serious AEs were reported in 38 patients (38%). AEs required discontinuation in 6 patients (6%) because of second primary cancers (n = 4) and infection (n = 2). Grade ≥3 events of special interest included infection (15%), hypertension (11%), bleeding events (3%), and atrial fibrillation (2%). Durable efficacy and long-term safety of acalabrutinib in this trial support its use in clinical management of symptomatic, untreated patients with CLL.

A randomized phase 2 trial of pembrolizumab versus pembrolizumab and acalabrutinib in patients with platinum-resistant metastatic urothelial cancer.

BACKGROUND: Inhibition of the programmed cell death protein 1 (PD-1) pathway has demonstrated clinical benefit in metastatic urothelial cancer (mUC); however, response rates of 15% to 26% highlight the need for more effective therapies. Bruton tyrosine kinase (BTK) inhibition may suppress myeloid-derived suppressor cells (MDSCs) and improve T-cell activation. METHODS: The Randomized Phase 2 Trial of Acalabrutinib and Pembrolizumab Immunotherapy Dual Checkpoint Inhibition in Platinum-Resistant Metastatic Urothelial Carcinoma (RAPID CHECK; also known as ACE-ST-005) was a randomized phase 2 trial evaluating the PD-1 inhibitor pembrolizumab with or without the BTK inhibitor acalabrutinib for patients with platinum-refractory mUC. The primary objectives were safety and objective response rates (ORRs) according to the Response Evaluation Criteria in Solid Tumors, version 1.1. Secondary endpoints included progression-free survival (PFS) and overall survival (OS). Immune profiling was performed to analyze circulating monocytic MDSCs and T cells. RESULTS: Seventy-five patients were treated with pembrolizumab (n = 35) or pembrolizumab plus acalabrutinib (n = 40). The ORR was 26% with pembrolizumab (9% with a complete response [CR]) and 20% with pembrolizumab plus acalabrutinib (10% with a CR). The grade 3/4 adverse events (AEs) that occurred in ≥15% of the patients were anemia (20%) with pembrolizumab and fatigue (23%), increased alanine aminotransferase (23%), urinary tract infections (18%), and anemia (18%) with pembrolizumab plus acalabrutinib. One patient treated with pembrolizumab plus acalabrutinib had high MDSCs at the baseline, which significantly decreased at week 7. Overall, MDSCs were not correlated with a clinical response, but some subsets of CD8+ T cells did increase during the combination treatment. CONCLUSIONS: Both treatments were generally well tolerated, although serious AE rates were higher with the combination. Acalabrutinib plus pembrolizumab did not improve the ORR, PFS, or OS in comparison with pembrolizumab alone in mUC. Baseline and on-treatment peripheral monocytic MDSCs were not different in the treatment cohorts. Proliferating CD8+ T-cell subsets increased during treatment, particularly in the combination cohort. Ongoing studies are correlating these peripheral immunome findings with tissue-based immune cell infiltration.

Inhibition of Bruton tyrosine kinase in patients with severe COVID-19.

Patients with severe COVID-19 have a hyperinflammatory immune response suggestive of macrophage activation. Bruton tyrosine kinase (BTK) regulates macrophage signaling and activation. Acalabrutinib, a selective BTK inhibitor, was administered off-label to 19 patients hospitalized with severe COVID-19 (11 on supplemental oxygen; 8 on mechanical ventilation), 18 of whom had increasing oxygen requirements at baseline. Over a 10-14 day treatment course, acalabrutinib improved oxygenation in a majority of patients, often within 1-3 days, and had no discernable toxicity. Measures of inflammation - C-reactive protein and IL-6 - normalized quickly in most patients, as did lymphopenia, in correlation with improved oxygenation. At the end of acalabrutinib treatment, 8/11 (72.7%) patients in the supplemental oxygen cohort had been discharged on room air, and 4/8 (50%) patients in the mechanical ventilation cohort had been successfully extubated, with 2/8 (25%) discharged on room air. Ex vivo analysis revealed significantly elevated BTK activity, as evidenced by autophosphorylation, and increased IL-6 production in blood monocytes from patients with severe COVID-19 compared with blood monocytes from healthy volunteers. These results suggest that targeting excessive host inflammation with a BTK inhibitor is a therapeutic strategy in severe COVID-19 and has led to a confirmatory international prospective randomized controlled clinical trial.

Acalabrutinib with or without obinutuzumab versus chlorambucil and obinutuzmab for treatment-naive chronic lymphocytic leukaemia (ELEVATE TN): a randomised, controlled, phase 3 trial.

BACKGROUND: Acalabrutinib is a selective, covalent Bruton tyrosine-kinase inhibitor with activity in chronic lymphocytic leukaemia. We compare the efficacy of acalabrutinib with or without obinutuzumab against chlorambucil with obinutuzumab in patients with treatment-naive chronic lymphocytic leukaemia. METHODS: ELEVATE TN is a global, phase 3, multicentre, open-label study in patients with treatment-naive chronic lymphocytic leukaemia done at 142 academic and community hospitals in 18 countries. Eligible patients had untreated chronic lymphocytic leukaemia and were aged 65 years or older, or older than 18 years and younger than 65 years with creatinine clearance of 30-69 mL/min (calculated by use of the Cockcroft-Gault equation) or Cumulative Illness Rating Scale for Geriatrics score greater than 6. Additional criteria included an Eastern Cooperative Oncology Group performance status score of 2 or less and adequate haematologic, hepatic, and renal function. Patients with significant cardiovascular disease were excluded, and concomitant treatment with warfarin or equivalent vitamin K antagonists was prohibited. Patients were randomly assigned (1:1:1) centrally via an interactive voice or web response system to receive acalabrutinib and obinutuzumab, acalabrutinib monotherapy, or obinutuzumab and oral chlorambucil. Treatments were administered in 28-day cycles. To reduce infusion-related reactions, acalabrutinib was administered for one cycle before obinutuzumab administration. Oral acalabrutinib was administered (100 mg) twice a day until progressive disease or unacceptable toxic effects occurred. In the acalabrutinib-obinutuzumab group, intravenous obinutuzumab was given on days 1 (100 mg), 2 (900 mg), 8 (1000 mg), and 15 (1000 mg) of cycle 2 and on day 1 (1000 mg) of cycles 3-7. In the obinutuzumab-chlorambucil group, intravenous obinutuzumab was given on days 1 (100 mg), 2 (900 mg), 8 (1000 mg), and 15 (1000 mg) of cycle 1 and on day 1 (1000 mg) of cycles 2-6. Oral chlorambucil was given (0·5 mg/kg) on days 1 and 15 of each cycle, for six cycles. The primary endpoint was progression-free survival between the two combination-therapy groups, assessed by independent review committee. Crossover to acalabrutinib was allowed in patients who progressed on obinutuzumab-chlorambucil. Safety was assessed in all patients who received at least one dose of treatment. Enrolment for this trial is complete, and the study is registered at ClinicalTrials.gov, NCT02475681. FINDINGS: Between Sept 14, 2015, and Feb 8, 2017, we recruited 675 patients for assessment. 140 patients did not meet eligibility criteria, and 535 patients were randomly assigned to treatment. 179 patients were assigned to receive acalabrutinib-obinutuzumab, 179 patients were assigned to receive acalabrutinib monotherapy, and 177 patients were assigned to receive obinutuzumab-chlorambucil. At median follow-up of 28·3 months (IQR 25·6-33·1), median progression-free survival was longer with acalabrutinib-obinutuzumab and acalabrutinib monotherapy, compared with obinutuzumab-chlorambucil (median not reached with acalabrutinib and obinutuzumab vs 22·6 months with obinutuzumab, hazard ratio [HR] 0·1; 95% CI 0·06-0·17, p<0·0001; and not reached with acalabrutinib monotherapy vs 22·6 months with obinutuzumab, 0·20; 0·13-0·3, p<0·0001). Estimated progression-free survival at 24 months was 93% with acalabrutinib-obinutuzumab (95% CI 87-96%), 87% with acalabrutinib monotherapy (81-92%), and 47% with obinutuzumab-chlorambucil (39-55%). The most common grade 3 or higher adverse event across groups was neutropenia (53 [30%] of 178 patients in the acalabrutinib-obinutuzumab group, 17 [9%] of 179 patients in the acalabrutinib group, and 70 [41%] of 169 patients in the obinutuzumab-chlorambucil group). All-grade infusion reactions were less frequent with acalabrutinib-obinutuzumab (24 [13%] of 178 patients) than obinutuzumab-chlorambucil (67 [40%] of 169 patients). Grade 3 or higher infections occurred in 37 (21%) patients given acalabrutinib-obinutuzumab, 25 (14%) patients given acalabrutinib monotherapy, and 14 (8%) patients given obinutuzumab-chlorambucil. Deaths occurred in eight (4%) patients given acalabrutinib-obinutuzumab, 12 (7%) patients given acalabrutinib, and 15 (9%) patients given obinutuzumab-chlorambucil. INTERPRETATION: Acalabrutinib with or without obinutuzumab significantly improved progression-free survival over obinutuzumab-chlorambucil chemoimmunotherapy, providing a chemotherapy-free treatment option with an acceptable side-effect profile that was consistent with previous studies. These data support the use of acalabrutinib in combination with obinutuzumab or alone as a new treatment option for patients with treatment-naive symptomatic chronic lymphocytic leukaemia. FUNDING: Acerta Pharma, a member of the AstraZeneca Group, and R35 CA198183 (to JCB).

Clinical and biological implications of target occupancy in CLL treated with the BTK inhibitor acalabrutinib.

Inhibition of the B-cell receptor pathway, and specifically of Bruton tyrosine kinase (BTK), is a leading therapeutic strategy in B-cell malignancies, including chronic lymphocytic leukemia (CLL). Target occupancy is a measure of covalent binding to BTK and has been applied as a pharmacodynamic parameter in clinical studies of BTK inhibitors. However, the kinetics of de novo BTK synthesis, which determines occupancy, and the relationship between occupancy, pathway inhibition and clinical outcomes remain undefined. This randomized phase 2 study investigated the safety, efficacy, and pharmacodynamics of a selective BTK inhibitor acalabrutinib at 100 mg twice daily (BID) or 200 mg once daily (QD) in 48 patients with relapsed/refractory or high-risk treatment-naïve CLL. Acalabrutinib was well tolerated and yielded an overall response rate (ORR) of partial response or better of 95.8% (95% confidence interval [CI], 78.9-99.9) and an estimated progression-free survival (PFS) rate at 24 months of 91.5% (95% CI, 70.0-97.8) with BID dosing and an ORR of 79.2% (95% CI, 57.9-92.9) and an estimated PFS rate at 24 months of 87.2% (95% CI, 57.2-96.7) with QD dosing. BTK resynthesis was faster in patients with CLL than in healthy volunteers. BID dosing maintained higher BTK occupancy and achieved more potent pathway inhibition compared with QD dosing. Small increments in occupancy attained by BID dosing relative to QD dosing compounded over time to augment downstream biological effects. The impact of BTK occupancy on long-term clinical outcomes remains to be determined. This trial was registered at www.clinicaltrials.gov as #NCT02337829.

Pharmacodynamic Analysis of BTK Inhibition in Patients with Chronic Lymphocytic Leukemia Treated with Acalabrutinib.

PURPOSE: To determine the pharmacodynamic relationship between target occupancy of Bruton tyrosine kinase (BTK) and inhibition of downstream signaling. PATIENTS AND METHODS: Patients with chronic lymphocytic leukemia (CLL) enrolled in a phase II clinical trial (NCT02337829) with the covalent, selective BTK inhibitor acalabrutinib donated blood samples for pharmacodynamic analyses. Study design included randomization to acalabrutinib 100 mg twice daily or 200 mg once daily and dose interruptions on day 4 and 5 of the first week. BTK occupancy and readouts of intracellular signaling were assessed sequentially between 4 and 48 hours from last dose. RESULTS: Four hours from last dose, BTK occupancy exceeded 96% and at trough, was higher with twice daily, median 95.3%, than with once daily dosing, median 87.6% (P < 0.0001). By 48 hours from last dose, median free BTK increased to 25.6%. Due to covalent binding of acalabrutinib, free BTK is generated by de novo synthesis. The estimated rate of BTK synthesis varied widely between patients ranging from 3.6% to 31.4% per day. Acalabrutinib reduced phosphorylation of BTK and inhibited downstream B-cell receptor (BCR) and NFκB signaling. During dosing interruptions up to 48 hours, expression of BCR target genes rebounded, while phosphorylation of signaling molecules remained repressed. In vitro cross-linking of IgM on CLL cells obtained 36 to 48 hours from last dose upregulated CD69, with high correlation between cellular free BTK and response (R = 0.7, P ≤ 0.0001). CONCLUSIONS: Higher BTK occupancy was achieved with twice daily over once daily dosing, resulting in deeper and more sustained inhibition of BCR signaling.