Preclinical characterization of pirtobrutinib, a highly selective, noncovalent (reversible) BTK inhibitor.

Bruton tyrosine kinase (BTK), a nonreceptor tyrosine kinase, is a major therapeutic target for B-cell-driven malignancies. However, approved covalent BTK inhibitors (cBTKis) are associated with treatment limitations because of off-target side effects, suboptimal oral pharmacology, and development of resistance mutations (eg, C481) that prevent inhibitor binding. Here, we describe the preclinical profile of pirtobrutinib, a potent, highly selective, noncovalent (reversible) BTK inhibitor. Pirtobrutinib binds BTK with an extensive network of interactions to BTK and water molecules in the adenosine triphosphate binding region and shows no direct interaction with C481. Consequently, pirtobrutinib inhibits both BTK and BTK C481 substitution mutants in enzymatic and cell-based assays with similar potencies. In differential scanning fluorimetry studies, BTK bound to pirtobrutinib exhibited a higher melting temperature than cBTKi-bound BTK. Pirtobrutinib, but not cBTKis, prevented Y551 phosphorylation in the activation loop. These data suggest that pirtobrutinib uniquely stabilizes BTK in a closed, inactive conformation. Pirtobrutinib inhibits BTK signaling and cell proliferation in multiple B-cell lymphoma cell lines, and significantly inhibits tumor growth in human lymphoma xenografts in vivo. Enzymatic profiling showed that pirtobrutinib was highly selective for BTK in >98% of the human kinome, and in follow-up cellular studies pirtobrutinib retained >100-fold selectivity over other tested kinases. Collectively, these findings suggest that pirtobrutinib represents a novel BTK inhibitor with improved selectivity and unique pharmacologic, biophysical, and structural attributes with the potential to treat B-cell-driven cancers with improved precision and tolerability. Pirtobrutinib is being tested in phase 3 clinical studies for a variety of B-cell malignancies.

The Role of Angiogenesis in Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) accounts for about 90% of all primary liver cancers and is the second leading cause of cancer-related deaths worldwide. The hypervascular nature of most HCC tumors underlines the importance of angiogenesis in the pathobiology of these tumors. Several angiogenic pathways have been identified as being dysregulated in HCC, suggesting they may be involved in the development and pathogenesis of HCC. These data provide practical targets for systemic treatments such as those targeting the vascular endothelial growth factor receptor and its ligand. However, the clinical relevance of other more recently identified angiogenic pathways in HCC pathogenesis or treatment remains unclear. Research into molecular profiles and validation of prognostic or predictive biomarkers will be required to identify the patient subsets most likely to experience meaningful benefit from this important class of agents.

Ramucirumab as second-line treatment in patients with advanced hepatocellular carcinoma following first-line therapy with sorafenib: Patient-focused outcome results from the randomised phase III REACH study.

PURPOSE: To report patient-focused outcomes as measured by quality of life (QoL) and performance status (PS) in REACH, a phase III placebo-controlled randomised study, assessing ramucirumab in advanced hepatocellular carcinoma (HCC) patients who received prior sorafenib. METHODS: Eligible patients had advanced HCC, Child-Pugh A, PS 0 or 1 and prior sorafenib. Patients received ramucirumab (8 mg/kg) or placebo (1:1) on day 1 of a 2-week cycle. QoL was assessed by FACT Hepatobiliary Symptom Index (FHSI)-8 and EuroQoL (EQ-5D) at baseline; cycles 4, 10, and 16; and end of treatment. PS was assessed at baseline, each cycle, and end of treatment. Deterioration in FHSI-8 was defined as a ≥3-point decrease from baseline and PS deterioration was defined as a change of ≥2. Both intention-to-treat and pre-specified subgroup of patients with baseline serum alpha-fetoprotein (AFP) ≥400 ng/mL were assessed. RESULTS: There were 565 patients randomised to ramucirumab and placebo. Compliance with FHSI and EQ-5D was high and similar between groups. In the ITT population, deterioration in FHSI-8, EQ-5D, and PS was similar between ramucirumab and placebo. In patients with baseline AFP ≥400 ng/mL, ramucirumab significantly reduced deterioration in FHSI-8 at the end of treatment compared with placebo (P = 0.0381), and there was a trend towards a delay in the deterioration of symptoms in FHSI-8 (HR 0.690; P = 0.054) and PS (HR 0.642; P = 0.057) in favour of ramucirumab. CONCLUSIONS: We report one of the most comprehensive data sets of QoL and symptom burden in patients undergoing systemic therapy for advanced HCC. Ramucirumab was associated with no worsening of QoL. In patients with baseline AFP ≥400 ng/mL, the significant survival benefit observed in patients treated with ramucirumab was coupled with a trend in patient-focused outcome benefits. CLINICAL TRIAL REGISTRATION: NCT01140347.

Ramucirumab versus placebo as second-line treatment in patients with advanced hepatocellular carcinoma following first-line therapy with sorafenib (REACH): a randomised, double-blind, multicentre, phase 3 trial.

BACKGROUND: VEGF and VEGF receptor-2-mediated angiogenesis contribute to hepatocellular carcinoma pathogenesis. Ramucirumab is a recombinant IgG1 monoclonal antibody and VEGF receptor-2 antagonist. We aimed to assess the safety and efficacy of ramucirumab in advanced hepatocellular carcinoma following first-line therapy with sorafenib. METHODS: In this randomised, placebo-controlled, double-blind, multicentre, phase 3 trial (REACH), patients were enrolled from 154 centres in 27 countries. Eligible patients were aged 18 years or older, had hepatocellular carcinoma with Barcelona Clinic Liver Cancer stage C disease or stage B disease that was refractory or not amenable to locoregional therapy, had Child-Pugh A liver disease, an Eastern Cooperative Oncology Group performance status of 0 or 1, had previously received sorafenib (stopped because of progression or intolerance), and had adequate haematological and biochemical parameters. Patients were randomly assigned (1:1) to receive intravenous ramucirumab (8 mg/kg) or placebo every 2 weeks, plus best supportive care, until disease progression, unacceptable toxicity, or death. Randomisation was stratified by geographic region and cause of liver disease with a stratified permuted block method. Patients, medical staff, investigators, and the funder were masked to treatment assignment. The primary endpoint was overall survival in the intention-to-treat population. This study is registered with ClinicalTrials.gov, number NCT01140347. FINDINGS: Between Nov 4, 2010, and April 18, 2013, 565 patients were enrolled, of whom 283 were assigned to ramucirumab and 282 were assigned to placebo. Median overall survival for the ramucirumab group was 9·2 months (95% CI 8·0-10·6) versus 7·6 months (6·0-9·3) for the placebo group (HR 0·87 [95% CI 0·72-1·05]; p=0·14). Grade 3 or greater adverse events occurring in 5% or more of patients in either treatment group were ascites (13 [5%] of 277 patients treated with ramucirumab vs 11 [4%] of 276 patients treated with placebo), hypertension (34 [12%] vs ten [4%]), asthenia (14 [5%] vs five [2%]), malignant neoplasm progression (18 [6%] vs 11 [4%]), increased aspartate aminotransferase concentration (15 [5%] vs 23 [8%]), thrombocytopenia (13 [5%] vs one [<1%]), hyperbilirubinaemia (three [1%] vs 13 [5%]), and increased blood bilirubin (five [2%] vs 14 [5%]). The most frequently reported (≥1%) treatment-emergent serious adverse event of any grade or grade 3 or more was malignant neoplasm progression. INTERPRETATION: Second-line treatment with ramucirumab did not significantly improve survival over placebo in patients with advanced hepatocellular carcinoma. No new safety signals were noted in eligible patients and the safety profile is manageable. FUNDING: Eli Lilly and Co.