Targeting Solid Tumors With BTK Inhibitors

The repurposing of FDA-approved Bruton’s tyrosine kinase (BTK) inhibitors as therapeutic agents for solid tumors may offer renewed hope for chemotherapy-resistant cancer patients. Here we review the emerging evidence regarding the clinical potential of BTK inhibitors in solid tumor therapy. The use of BTK inhibitors may through lead optimization and translational research lead to the development of new and effective combination regimens for metastatic and/or therapy-refractory solid tumor patients.

Development and validation of a targeted sequencing panel for application to treatment-refractory solid tumor.

245 Background: Next generation sequencing has revolutionised genomic studies of cancer, having facilitated the development of precision oncology treatments based on a tumour’s molecular profile. We aimed to develop a targeted sequencing panel for application to treatment-refractory solid tumor types with particular focus on tumours of the stomach cancer, plus test for utility in FFPE, fluid sample and cancer cell lines. Methods: “CancerMaster” is custom RNA probes for target enrichment sequencing. It consists of all unions (7,811 regions, 2.5Mb) of reported exons of 524 tumor and immune related genes. The panel contains special RNA probes, which enables detection of microsatellite instability, Epstein-Barr virus and Human papillomavirus. Also, the CancerMaster panel analyzes 524 genes as well as genomic signatures including microsatellite instability (MSI), tumor mutational burden (TMB) and HLA allele. FFPE samples and 49 gastric cancer (GC) cell lines were collected for performance and application testing. Panel sensitivity and precision were measured using well-characterised DNA controls (n = 117), and specificity by Sanger sequencing, pyrosequencing, FoundationOne CDx. Results: We achieved a mean coverage of 1,032x, with sensitivity and specificity of >99% and precision of >97%. In this study, we evaluated 26 Yonsei Cancer Center (YCC) GC cell lines and 23 GC cell lines from other sources (ATCC, KCLB, and JCRB). Application to 49 gastric cancers cell lines resulted in detection of copy number variant (CNV), single number variant (SNV) and small InDel aligned to whole exome sequencing data. In addition to previous novel EBV infected cell line (YCCEL1/YCC-10, J Gen Virol. 2013), we observed amplification and overexpression of receptor tyrosine kinase (RTK) including HER2 (YCC-19, 32, 33, 38), EGFR (YCC-11, 21), Met (YCC-31, 34), and FGFR2 (YCC-28, 30) in YCC GC cell lines; confirming that protein was overexpression by Western blot or Flow cytometry in 19/49 (38.8%). Interestingly, amplification of RTKs was detected mutually exclusive pattern with other RTK amplification. Conclusions: We have developed and validated an analytically-validated panel for application to cancers of treatment-refractory types.

A phase I study of APL-501, an anti-PD-1 antibody, in patients with recurrent or advanced solid tumors.

e15125 Background: APL-501 is a humanized monoclonal antibody targeting programmed cell death-1 (PD-1). APL-501 is being evaluated in patients (pts) with advanced recurrent and relapsed solid tumors who had not been previously treated with an immune checkpoint inhibitor in an ongoing 3-part Phase 1 trial (NCT03053466). Herein, we present the emerging pharmacokinetic (PK) and receptor occupancy (RO), safety and preliminary efficacy. Methods: Weight-based dose escalation (1, 3, and 10 mg/kg, Part 1) and Extension (Part 2) has been completed and the study is currently enrolling specific tumor types (MSI-H/dMMR and Carcinoma of Unknown Primary [CUP]) into the Expansion Cohorts (Part 3). Relapsed/refractory solid tumor pts were enrolled in Part 1 and Part 2. Key exclusion criteria included prior therapy targeting PD-1/PD-L1 and uncontrolled CNS metastases. APL-501 was administered IV over 1 hour every 14 days. Serum and PBMCs were collected for PK and RO analysis, respectively. RO was assessed using different T-cell markers measured by flow cytometry of PBMC. Anti-tumor activity was assessed by investigators using RECIST and irRECIST. Safety was assessed using CTCAE, v4.03. Results: As of 31 Dec 2019, 22 pts were enrolled with a mean age of 62.1 (SD: 12.2) years. ECOG PS 0/1 reported at 10/12 pts, respectively. Pts had a median number of 3 prior lines of therapy (range, 1 – 9) and median time to treatment from initial diagnosis was 30.1 months (range, 6.7 – 184.8). Across doses evaluated, APL-501 demonstrated dose proportional PK. One hundred percent (100%) RO was observed across all doses evaluated. No dose limiting toxicities were reported. Fifteen pts (68.2%) had related AEs; two pts (9.1%) had Grade ≥ 3 related AEs to APL-501. Eight pts had stable disease and two pts had partial response by RECIST (esophageal adenocarcinoma and CUP). Seven pts remained on therapy for ≥ 24 weeks. The recommended phase 2 dose (RP2D) has been determined to be 400 mg IV every 14 days (non-weight-based) based on safety and PK modeling. Conclusions: Preliminary results indicate clinical activity of APL-501 in relapsed/refractory malignant disease with a generally tolerable safety profile. The PK and RO profile, across all doses evaluated, appears comparable to marketed PD-1 inhibitors. Continued exploration of APL-501 with the RP2D in CUP and MSI-H/dMMR tumors is being planned. Clinical trial information: NCT03053466 .

First-in-human phase I trial of anti-hepatocyte growth factor (HGF) antibody (YYB101) in refractory solid tumor patients: Integrative pathologic-genomic analysis and the final results.

3104 Background: It has been demonstrated in vivo that HGF-MET signaling axis is a key molecular determinant in tumor invasion and there is a significant association in HGF expression and mesenchymal phenotype in addition to immune cell recruitment. We have developed a HGF neutralizing humanized monoclonal antibody antibody, YYB-101. The aim of this study was to determine the maximum tolerate dose (MTD), safety, pharmacokinetics (PK), and pharmacodynamics (PD) of YYB101, in patients with refractory solid tumors. Methods: YYB101 was administered intravenously at once every 2 weeks doses of 0.3, 1, 3, 5, 10, 20, 30 mg/kg, according to a 3+3 dose escalation design. Enrolled patients were planned to receive YYB101 until disease progression or intolerable toxicity. The escalation and expansion cohorts (20mg/kg) were completed. Pre-planned biomarker analysis was performed in parallel. Results: 39 heavily pre-treated refractory cancer patients were enrolled and received YYB101. No DLT was observed. YYB101 demonstrated dose proportional PK up to the dose of 30 mg/kg. No patients discontinued treatment because of adverse events. Based on PK analysis and toxicity data, the recommended dose was determined as 20 mg/kg. Of 39 evaluation patients, there was 1 confirmed partial response for > +14months (2.5%, N = 1; 1 (of 2) sebaceous carcinoma) and 17 stable disease as best response (43.5%, N = 17; 7 (of 13) CRC, 3 (of 4) melanoma, 1 (of 2) sebaceous carcinoma, 1 (of 3) gastric, 1 (of 1) basal cell carcinoma, 2 (of 10) ovarian cancer, 1 (of 1) HCC, 1 (of 1) lung cancer). Of note, 1 sebaceous carcinoma patient who have failed to ≥2+ lines of chemotherapy, have been responding to YYB for 14 months. The MET and HGF expressions by immunohistochemistry (IHC) were evaluated in 19 and 17 tumor specimens, respectively. Neither protein expressions were significant predictors for treatment response to anti-HGF antibody. However, we have observed significant reduction in HGF in responders to YYB. Two long-term responders had mesenchymal signature in RNA sequencing. Conclusions: YYB101 has a favorable safety profile in patients with refractory solid tumors and a dose-proportional PK. Efficacy data are encouraging and phase II combination therapy with YYB101 is planned to be open in metastatic CRC patients as salvage treatment. The predictive power of mesenchymal signature in YYB responders will be defined prospectively. Clinical trial information: 02499224.

A dose-escalation study of imipridone ONC201 administered every one (QW) or three weeks (Q3W) in advanced solid tumors and multiple myeloma.

2592 Background: ONC201 is an orally active, first-in-class small molecule activator of the integrated stress response that selectively upregulates ATF4 to trigger tumor cell death. A phase I study of ONC201 exploring different dosing regimens and drug exposure was conducted to determine the maximum tolerated dose (MTD), and recommended phase II dose (RP2D). Methods: A modified accelerated-titration dose escalation design was employed to enroll patients onto 2 sequential dose-escalation arms: ONC201 Q3W and QW. Dose escalation proceeded with the following order: 125, 250, 500, and 625mg (Q3W) and 250, 375, 500 and 625 (QW). Dose exposure ranged from 125 mg/6 wks to 1875 mg/3 wks. Key eligibility: advance/refractory solid tumor or myeloma, ECOG 0/1, and no active CNS disease. Adverse events, SAEs, laboratory values, physical exam findings, EKGs and bio-samples (for PK/PD) are collected. Pre and post ONC201 dose biopsies are being obtained from the 500mg weekly cohort and above. Results: 17 pts (12F:5M) with treatment-refractory tumors have been enrolled to date. Dose/#pts Q3W: 125/6, 250/1, 500/1, and 625/1; QW: 250/4, 375/4. Two patients have been enrolled at 500mg QW after database lock and not included in this assessment. Median (range) age: 57 yrs (27-72). ECOG 0/1: 2/15. MTD has not been reached. No DLTs observed. Tumor types: 8 CRC, 3 pancreatic, 2 sarcoma and 1 each cervical, endometrial, NSCLC (adeno) and small bowel. Of 17 pts, 10 (59%) had ≥1 tx-related adverse events (TRAEs), possibly related. Most common TRAEs (≥15% pts): fatigue (9,53%), anorexia (5,29%), nausea (4,24%), vomiting (4,24%), abdominal pain (3,18%), and arthralgias (2,12%). Grade ≥ 3 TRAEs were observed in 3 pts (18%). Pharmacokinetic and pharmacodynamic analysis is ongoing. Fresh frozen and paraffin-embedded biopsies (baseline and week 2) are being assessed for tumor markers implicated in the mechanism of action. No objective responses by RECIST have been seen. Final cohort is enrolling. Conclusions: ONC201 was well tolerated throughout the Q3W dosing and weekly dosing has been well tolerated to date without an apparent increase in AEs. Final enrollment summary, AEs and PK/PD data will be presented. Clinical trial information: NCT02609230.

Phase 1/2 KEYNOTE-051 study of pembrolizumab (pembro) in pediatric patients (pts) with advanced melanoma or a PD-L1+ advanced, relapsed, or refractory solid tumor or lymphoma.

10525 Background: In phase 1 of the KEYNOTE-051 study (NCT02332668), the 2 mg/kg Q3W approved adult dose of pembro was also determined to be the pediatric recommended phase 2 dose. In phase 2, presented herein, we further evaluated this dose in pediatric pts with advanced cancer. Methods: Children aged 6 mo to < 18 y with advanced melanoma or a PD-L1+ advanced, relapsed or refractory solid tumor or lymphoma, measurable disease per RECIST v1.1, and performance score ≥50 using Lansky Play or Karnofsky scales received pembro 2 mg/kg Q3W for 35 cycles or until confirmed disease progression per immune-related RECIST by investigator review, intolerable toxicity, or pt/investigator decision to discontinue. Tumor imaging was performed every 8 wk for the first 6 mo, then every 12 wk thereafter. AEs were graded by NCI CTCAE v4.0. Key efficacy endpoints were ORR, disease control rate (DCR), and PFS per RECIST v1.1 by investigator and OS. Results: Of 369 pts prescreened, 364 were evaluable for PD-L1 expression; of these, 121 (33.2%) were PD-L1+. 66 pts were enrolled; median follow-up was 2.5 mo (range, 0.2-18). As of the data cutoff (Nov 7, 2016), 23 (34.8%) pts were still on treatment. Median age was 13 y (range, 1-17), 77.3% had metastatic disease, and 34.8% had ≥3 prior lines of therapy for recurrent/metastatic disease. Primary diagnoses were non-CNS solid tumors (n = 45), CNS tumors (n = 16), and lymphoma (n = 5). 5 (7.6%) pts had grade 3-4 treatment-related AEs (TRAEs), most commonly neutropenia (n = 2). No treatment-related deaths occurred; 1 pt discontinued for a TRAE (grade 3 AST increased). 1 pt each with Hodgkin lymphoma, adrenocortical carcinoma, mesothelioma, and glioblastoma had partial response for an ORR of 6.1% (95% CI, 1.7-14.8); 7 (10.6%) pts had stable disease for a DCR of 16.7% (95% CI, 8.6-27.9). Median PFS and OS were 1.8 mo and 9.2 mo, respectively; 12-mo PFS was 10.2% and OS was 40.5%. Potential effects of pembro on the developing immune system (eg, T and B cells, vaccinated antibodies) will also be presented. Conclusions: Pembro showed low toxicity and warrants further study to determine activity in select pediatric tumors. Enrollment in KEYNOTE-051 is ongoing. Clinical trial information: NCT02332668.