Enhancer retargeting of CDX2 and UBTF::ATXN7L3 define a subtype of high-risk B-progenitor acute lymphoblastic leukemia.

Transcriptome sequencing has identified multiple subtypes of B-progenitor acute lymphoblastic leukemia (B-ALL) of prognostic significance, but a minority of cases lack a known genetic driver. Here, we used integrated whole-genome (WGS) and -transcriptome sequencing (RNA-seq), enhancer mapping, and chromatin topology analysis to identify previously unrecognized genomic drivers in B-ALL. Newly diagnosed (n = 3221) and relapsed (n = 177) B-ALL cases with tumor RNA-seq were studied. WGS was performed to detect mutations, structural variants, and copy number alterations. Integrated analysis of histone 3 lysine 27 acetylation and chromatin looping was performed using HiChIP. We identified a subset of 17 newly diagnosed and 5 relapsed B-ALL cases with a distinct gene expression profile and 2 universal and unique genomic alterations resulting from aberrant recombination-activating gene activation: a focal deletion downstream of PAN3 at 13q12.2 resulting in CDX2 deregulation by the PAN3 enhancer and a focal deletion of exons 18-21 of UBTF at 17q21.31 resulting in a chimeric fusion, UBTF::ATXN7L3. A subset of cases also had rearrangement and increased expression of the PAX5 gene, which is otherwise uncommon in B-ALL. Patients were more commonly female and young adult with median age 35 (range,12-70 years). The immunophenotype was characterized by CD10 negativity and immunoglobulin M positivity. Among 16 patients with known clinical response, 9 (56.3%) had high-risk features including relapse (n = 4) or minimal residual disease >1% at the end of remission induction (n = 5). CDX2-deregulated, UBTF::ATXN7L3 rearranged (CDX2/UBTF) B-ALL is a high-risk subtype of leukemia in young adults for which novel therapeutic approaches are required.

Talazoparib monotherapy in metastatic castration-resistant prostate cancer with DNA repair alterations (TALAPRO-1): an open-label, phase 2 trial.

BACKGROUND: Poly(ADP-ribose) polymerase (PARP) inhibitors have antitumour activity against metastatic castration-resistant prostate cancers with DNA damage response (DDR) alterations in genes involved directly or indirectly in homologous recombination repair (HRR). In this study, we assessed the PARP inhibitor talazoparib in metastatic castration-resistant prostate cancers with DDR-HRR alterations. METHODS: In this open-label, phase 2 trial (TALAPRO-1), participants were recruited from 43 hospitals, cancer centres, and medical centres in Australia, Austria, Belgium, Brazil, France, Germany, Hungary, Italy, the Netherlands, Poland, Spain, South Korea, the UK, and the USA. Patients were eligible if they were men aged 18 years or older with progressive, metastatic, castration-resistant prostate cancers of adenocarcinoma histology, measurable soft-tissue disease (per Response Evaluation Criteria in Solid Tumors version 1.1 [RECIST 1.1]), an Eastern Cooperative Oncology Group performance status of 0-2, DDR-HRR gene alterations reported to sensitise to PARP inhibitors (ie, ATM, ATR, BRCA1, BRCA2, CHEK2, FANCA, MLH1, MRE11A, NBN, PALB2, RAD51C), had received one or two taxane-based chemotherapy regimens for metastatic disease, and progressed on enzalutamide or abiraterone, or both, for metastatic castration-resistant prostate cancers. Eligible patients were given oral talazoparib (1 mg per day; or 0·75 mg per day in patients with moderate renal impairment) until disease progression, unacceptable toxicity, investigator decision, withdrawal of consent, or death. The primary endpoint was confirmed objective response rate, defined as best overall soft-tissue response of complete or partial response per RECIST 1.1, by blinded independent central review. The primary endpoint was assessed in patients who received study drug, had measurable soft-tissue disease, and had a gene alteration in one of the predefined DDR-HRR genes. Safety was assessed in all patients who received at least one dose of the study drug. This study is registered with ClinicalTrials.gov, NCT03148795, and is ongoing. FINDINGS: Between Oct 18, 2017, and March 20, 2020, 128 patients were enrolled, of whom 127 received at least one dose of talazoparib (safety population) and 104 had measurable soft-tissue disease (antitumour activity population). Data cutoff for this analysis was Sept 4, 2020. After a median follow-up of 16·4 months (IQR 11·1-22·1), the objective response rate was 29·8% (31 of 104 patients; 95% CI 21·2-39·6). The most common grade 3-4 treatment-emergent adverse events were anaemia (39 [31%] of 127 patients), thrombocytopenia (11 [9%]), and neutropenia (ten [8%]). Serious treatment-emergent adverse events were reported in 43 (34%) patients. There were no treatment-related deaths. INTERPRETATION: Talazoparib showed durable antitumour activity in men with advanced metastatic castration-resistant prostate cancers with DDR-HRR gene alterations who had been heavily pretreated. The favourable benefit-risk profile supports the study of talazoparib in larger, randomised clinical trials, including in patients with non-BRCA alterations. FUNDING: Pfizer/Medivation.

Cabozantinib for metastatic breast carcinoma: results of a phase II placebo-controlled randomized discontinuation study.

PURPOSE: Cabozantinib (XL184), a multi-targeted oral tyrosine kinase inhibitor with activity against MET, VEGFR2, AXL, and other tyrosine kinases, was assessed in a cohort of metastatic breast cancer (MBC) patients in a phase II randomized discontinuation trial (RDT). METHODS: Patients received 100 mg cabozantinib daily during a 12-week lead-in stage. Those with stable disease per modified Response Evaluation Criteria in Solid Tumors version 1.0 at 12 weeks were randomized to either continue cabozantinib or receive placebo. Primary endpoints were objective response rate (ORR) during the 12-week lead-in stage and progression-free survival (PFS) after randomization. Patients were also followed for overall survival (OS). RESULTS: Forty-five patients with MBC and a median of three prior lines of chemotherapy for metastatic disease were enrolled. The ORR during the lead-in stage was 13.6 % (95 % confidence interval [CI] 6-25.7 %), and the disease control rate at week 12 was 46.7 % (95 % CI 31.7-61.6 %). Per the initial RDT study design, patients with stable disease at week 12 were randomized to cabozantinib or placebo. Following a Study Oversight Committee recommendation, randomization was suspended. Patients in the lead-in stage continued on open-label cabozantinib. Patients in the randomization stage were subsequently unblinded. The overall median PFS for all MBC patients was 4.3 months. Median OS was 11.4 months (95 % CI 10.5-16.5 months). The most common grade 3/4 adverse events in the lead-in stage were palmar-plantar erythrodysesthesia (13 %) and fatigue (11 %). One death from respiratory failure was reported as drug-related during the lead-in stage. CONCLUSIONS: In heavily pretreated MBC patients, cabozantinib monotherapy demonstrated clinical activity including objective response and disease control.

Changes in plasma biomarkers following treatment with cabozantinib in metastatic castration-resistant prostate cancer: a post hoc analysis of an extension cohort of a phase II trial.

BACKGROUND: Cabozantinib is an orally available inhibitor of tyrosine kinases including VEGFR2 and c-MET. We performed a post hoc analysis to find associations between select plasma biomarkers and treatment response in patients (pts) with metastatic castration resistant prostate cancer (mCRPC) who received cabozantinib 100 mg daily as part of a phase 2 non-randomized expansion cohort (NCT00940225). METHODS: Plasma samples were collected at baseline, 6 weeks and at time of maximal response from 81 mCRPC pts with bone metastases, of which 33 also had measurable soft-tissue disease. Levels of 27 biomarkers were measured in duplicate using enzyme-linked immunosorbent assay. Spearman correlation coefficients were calculated for the association between biomarker levels or their change on treatment and either bone scan response (BSR) or soft tissue response according to RECIST. RESULTS: A BSR and RECIST response were seen in 66/81 pts (81 %) and 6/33 pts (18 %) respectively. No significant associations were found between any biomarker at any time point and either type of response. Plasma concentrations of VEGFA, FLT3L, c-MET, AXL, Gas6A, bone-specific alkaline phosphatase, interleukin-8 and the hypoxia markers CA9 and clusterin significantly increased during treatment with cabozantinib irrespective of response. The plasma concentrations of VEGFR2, Trap5b, Angiopoietin-2, TIMP-2 and TIE-2 significantly decreased during treatment with caboznatinib. CONCLUSIONS: Our data did not reveal plasma biomarkers associated with response to cabozantinib. The observed alterations in several biomarkers during treatment with cabozantinib may provide insights on the effects of cabozantinib on tumor cells and on tumor micro-environment and may help point to potential co-targeting approaches.

Neoadjuvant talazoparib in patients with germline BRCA1/2 mutation-positive, early-stage triple-negative breast cancer: exploration of tumor BRCA mutational status.

BACKGROUND: Talazoparib monotherapy in patients with germline BRCA-mutated, early-stage triple-negative breast cancer (TNBC) showed activity in the neoadjuvant setting in the phase II NEOTALA study (NCT03499353). These biomarker analyses further assessed the mutational landscape of the patients enrolled in the NEOTALA study. METHODS: Baseline tumor tissue from the NEOTALA study was tested retrospectively using FoundationOne®CDx. To further hypothesis-driven correlative analyses, agnostic heat-map visualizations of the FoundationOne®CDx tumor dataset were used to assess overall mutational landscape and identify additional candidate predictive biomarkers of response. RESULTS: All patients enrolled (N = 61) had TNBC. In the biomarker analysis population, 75.0% (39/52) and 25.0% (13/52) of patients exhibited BRCA1 and BRCA2 mutations, respectively. Strong concordance (97.8%) was observed between tumor BRCA and germline BRCA mutations, and 90.5% (38/42) of patients with tumor BRCA mutations evaluable for somatic-germline-zygosity were predicted to exhibit BRCA loss of heterozygosity (LOH). No patients had non-BRCA germline DNA damage response (DDR) gene variants with known/likely pathogenicity, based on a panel of 14 non-BRCA DDR genes. Ninety-eight percent of patients had TP53 mutations. Genomic LOH, assessed continuously or categorically, was not associated with response. CONCLUSION: The results from this exploratory biomarker analysis support the central role of BRCA and TP53 mutations in tumor pathobiology. Furthermore, these data support assessing germline BRCA mutational status for molecular eligibility for talazoparib in patients with TNBC.

Association of leukemic molecular profile with efficacy of inotuzumab ozogamicin in adults with relapsed/refractory ALL.

ABSTRACT: The phase 3 INO-VATE trial demonstrated higher rates of remission, measurable residual disease negativity, and improved overall survival for patients with relapsed/refractory (R/R) acute lymphoblastic leukemia (ALL) who received inotuzumab ozogamicin (InO) vs standard-of-care chemotherapy (SC). Here, we examined associations between genomic alterations and the efficacy of InO. Of 326 randomized patients, 91 (InO, n = 43; SC, n = 48) had samples evaluable for genomic analysis. The spectrum of gene fusions and other genomic alterations observed was comparable with prior studies of adult ALL. Responses to InO were observed in all leukemic subtypes, genomic alterations, and risk groups. Significantly higher rates of complete remission (CR)/CR with incomplete count recovery were observed with InO vs SC in patients with BCR::ABL1-like ALL (85.7% [6/7] vs 0% [0/5]; P = .0076), with TP53 alterations (100% [5/5] vs 12.5% [1/8]; P = .0047), and in the high-risk BCR::ABL1- (BCR::ABL1-like, low-hypodiploid, KMT2A-rearranged) group (83.3% [10/12] vs 10.5% [2/19]; P < .0001). This retrospective, exploratory analysis of the INO-VATE trial demonstrated potential for benefit with InO for patients with R/R ALL across leukemic subtypes, including BCR::ABL1-like ALL, and for those bearing diverse genomic alterations. Further confirmation of the efficacy of InO in patients with R/R ALL exhibiting the BCR::ABL1-like subtype or harboring TP53 alterations is warranted. This trial was registered at www.ClinicalTrials.gov as #NCT01564784.

First-line talazoparib with enzalutamide in HRR-deficient metastatic castration-resistant prostate cancer: the phase 3 TALAPRO-2 trial.

Preclinical evidence has suggested an interplay between the androgen receptor, which largely drives the growth of prostate cancer cells, and poly(ADP-ribose) polymerase. This association provides a rationale for their co-inhibition for the treatment of metastatic castration-resistant prostate cancer (mCRPC), an area of unmet medical need. The phase 3 TALAPRO-2 study investigated combining the poly(ADP-ribose) polymerase inhibitor talazoparib with enzalutamide versus enzalutamide alone as first-line treatment of mCRPC. Patients were prospectively assessed for tumor alterations in DNA damage response genes involved in homologous recombination repair (HRR). Two cohorts were enrolled sequentially: an all-comers cohort that was enrolled first (cohort 1; N = 805 (169 were HRR-deficient)), followed by an HRR-deficient-only cohort (cohort 2; N = 230). We present results from the alpha-controlled primary analysis for the combined HRR-deficient population (N = 399). Patients were randomized in a 1:1 ratio to talazoparib or placebo, plus enzalutamide. The primary endpoint, radiographic progression-free survival, was met (median not reached at the time of the analysis for the talazoparib group versus 13.8 months for the placebo group; hazard ratio, 0.45; 95% confidence interval, 0.33 to 0.61; P < 0.0001). Data for overall survival, a key secondary endpoint, are immature but favor talazoparib (hazard ratio, 0.69; 95% confidence interval, 0.46 to 1.03; P = 0.07). Common adverse events in the talazoparib group were anemia, fatigue and neutropenia. Combining talazoparib with enzalutamide significantly improved radiographic progression-free survival in patients with mCRPC harboring HRR gene alterations, supporting talazoparib plus enzalutamide as a potential first-line treatment for these patients. ClinicalTrials.gov Identifier: NCT03395197 .

Genomic analysis of advanced breast cancer tumors from talazoparib-treated gBRCA1/2mut carriers in the ABRAZO study.

These analyses explore the impact of homologous recombination repair gene mutations, including BRCA1/2 mutations and homologous recombination deficiency (HRD), on the efficacy of the poly(ADP-ribose) polymerase (PARP) inhibitor talazoparib in the open-label, two-cohort, Phase 2 ABRAZO trial in germline BRCA1/2-mutation carriers. In the evaluable intent-to-treat population (N = 60), 58 (97%) patients harbor ≥1 BRCA1/2 mutation(s) in tumor sequencing, with 95% (53/56) concordance between germline and tumor mutations, and 85% (40/47) of evaluable patients have BRCA locus loss of heterozygosity indicating HRD. The most prevalent non-BRCA tumor mutations are TP53 in patients with BRCA1 mutations and PIK3CA in patients with BRCA2 mutations. BRCA1- or BRCA2-mutated tumors show comparable clinical benefit within cohorts. While low patient numbers preclude correlations between HRD and efficacy, germline BRCA1/2 mutation detection from tumor-only sequencing shows high sensitivity and non-BRCA genetic/genomic events do not appear to influence talazoparib sensitivity in the ABRAZO trial.ClinicalTrials.gov identifier: NCT02034916.

The design, synthesis, and biological evaluation of PIM kinase inhibitors.

A series of substituted benzofuropyrimidinones with pan-PIM activities and excellent selectivity against a panel of diverse kinases is described. Initial exploration identified aryl benzofuropyrimidinones that were potent, but had cell permeability limitation. Using X-ray crystal structures of the bound PIM-1 complexes with 3, 5m, and 6d, we were able to guide the SAR and identify the alkyl benzofuropyrimidinone (6l) with good PIM potencies, permeability, and oral exposure.

Pyrazolopyrimidines as dual Akt/p70S6K inhibitors.

Activation of the PI3K/Akt/mTOR kinase pathway is frequently associated with human cancer. Selective inhibition of p70S6Kinase, which is the last kinase in the PI3K pathway, is not sufficient for strong tumor growth inhibition and can lead to activation of upstream proteins including Akt through relief of a negative feedback loop. Targeting multiple sites in the PI3K pathway might be beneficial for optimal activity. In this manuscript we report the design of dual Akt/p70S6K inhibitors and the evaluation of the lead compound 11b in vivo, which was eventually advanced into clinical development.

Determinants of Response to Talazoparib in Patients with HER2-Negative, Germline BRCA1/2-Mutated Breast Cancer.

PURPOSE: PARP inhibitors (PARPi) have demonstrated efficacy in tumors with germline breast cancer susceptibility genes (gBRCA) 1 and 2 mutations, but further factors influencing response to PARPi are poorly understood. EXPERIMENTAL DESIGN: Breast cancer tumor tissue from patients with gBRCA1/2 mutations from the phase III EMBRACA trial of the PARPi talazoparib versus chemotherapy was sequenced using FoundationOne CDx. RESULTS: In the evaluable intent-to-treat population, 96.1% (296/308) had ≥1 tumor BRCA (tBRCA) mutation and there was strong concordance (95.3%) between tBRCA and gBRCA mutational status. Genetic/genomic characteristics including BRCA loss of heterozygosity (LOH; identified in 82.6% of evaluable patients), DNA damage response (DDR) gene mutational burden, and tumor homologous recombination deficiency [assessed by genomic LOH (gLOH)] demonstrated no association with talazoparib efficacy. CONCLUSIONS: Overall, BRCA LOH status, DDR gene mutational burden, and gLOH were not associated with talazoparib efficacy; however, these conclusions are qualified by population heterogeneity and low patient numbers in some subgroups. Further investigation in larger patient populations is warranted.

Avelumab in Combination Regimens for Relapsed/Refractory DLBCL: Results from the Phase Ib JAVELIN DLBCL Study.

BACKGROUND: Relapsed/refractory (R/R) diffuse large B-cell lymphoma (DLBCL) is associated with a poor prognosis despite the availability of multiple treatment options. Preliminary evidence suggests that DLBCL may be responsive to programmed death ligand 1 (PD-L1)/programmed death 1 inhibitors. OBJECTIVE: The JAVELIN DLBCL study was conducted to assess whether a combination of agents could augment and sustain the antitumor immunity of avelumab, an anti-PD-L1 antibody, in R/R DLBCL. METHODS: This was a multicenter, randomized, open-label, parallel-arm study with a phase Ib and a phase III component. Reported here are the results from the phase Ib study, wherein 29 adult patients with DLBCL were randomized 1:1:1 to receive avelumab in combination with utomilumab (an immunoglobulin G2 4-1BB agonist) and rituximab (arm A), avelumab in combination with utomilumab and azacitidine (arm B), or avelumab in combination with bendamustine and rituximab (arm C). The primary endpoints were dose-limiting toxicities and objective response as assessed by the investigator per Lugano Response Classification criteria. RESULTS: Of the seven patients in arm A, one (14.3%) experienced two grade 3 dose-limiting toxicities (herpes zoster and ophthalmic herpes zoster); no dose-limiting toxicities were reported in arms B or C. No new safety concerns emerged for avelumab. One partial response was reported in arm A, three complete responses in arm C, and no responses in arm B. Given the insufficient antitumor activity in arms A and B and the infeasibility of expanding arm C, the study was discontinued before initiation of the phase III component. CONCLUSIONS: The low level of clinical activity suggests that PD-L1 inhibitor activity may be limited in R/R DLBCL. CLINICALTRIALS. GOV IDENTIFIER: NCT02951156.

Inotuzumab Ozogamicin for Relapsed/Refractory Acute Lymphoblastic Leukemia in the INO-VATE Trial: CD22 Pharmacodynamics, Efficacy, and Safety by Baseline CD22.

PURPOSE: We assessed the relationship between cluster of differentiation-22 (CD22) expression and outcomes of inotuzumab ozogamicin versus standard of care (SC) in INO-VATE (NCT01564784). PATIENTS AND METHODS: Adults with relapsed/refractory B-cell precursor CD22-positive (by local or central laboratory) acute lymphoblastic leukemia were randomized to inotuzumab ozogamicin (n = 164) or SC (n = 162). Outcomes were analyzed by baseline CD22 positivity (percentage of leukemic blasts CD22 positive, ≥90% vs. <90%) and CD22 receptor density [molecules of equivalent soluble fluorochrome (MESF), quartile analysis]. RESULTS: Most patients had high (≥90%) CD22 positivity per central laboratory. The response rate was significantly higher with inotuzumab ozogamicin versus SC. Minimal/measurable residual disease negativity, duration of remission (DoR), progression-free survival, and overall survival (OS) were significantly better with inotuzumab ozogamicin versus SC in patients with CD22 positivity ≥90%. Fewer patients had CD22 positivity <90%; for whom, response rates were higher with inotuzumab ozogamicin versus SC, but DoR and OS appeared similar. Similar trends were evident in quartile analyses of CD22 MESF and CD22 positivity per local laboratory. Among inotuzumab ozogamicin-responding patients with subsequent relapse, decrease in CD22 positivity and receptor density was evident, but not the emergence of CD22 negativity. Rates of grade ≥3 hematologic adverse events (AEs) were similar and hepatobiliary AEs rate was higher for inotuzumab ozogamicin versus SC. No apparent relationship was observed between the rates of hematologic and hepatic AEs and CD22 expression. CONCLUSIONS: Inotuzumab ozogamicin demonstrated a favorable benefit-risk profile versus SC in patients with higher and lower CD22 expression. Patients with high CD22 expression and normal cytogenetics benefited the most from inotuzumab ozogamicin therapy.

Impact of minimal residual disease status in patients with relapsed/refractory acute lymphoblastic leukemia treated with inotuzumab ozogamicin in the phase III INO-VATE trial.

Minimal residual disease (MRD) negativity is a key prognostic indicator of outcome in acute lymphocytic leukemia. In the INO-VATE trial (clinicaltrials.gov identifier: NCT01564784), patients with relapsed/refractory acute lymphocytic leukemia who received inotuzumab versus standard chemotherapy achieved greater remission and MRD-negativity rates as well as improved overall survival: hazard ratio 0.75, one-sided P = 0.0105. The current analysis assessed the prognostic value of MRD negativity at the end of inotuzumab treatment. All patients who received inotuzumab (n = 164) were included. Among patients with complete remission/complete remission with incomplete hematologic response (CR/CRi; n = 121), MRD-negative status (by multiparametric flow cytometry) was defined as <1 × 10-4 blasts/nucleated cells. MRD negativity was achieved in 76 patients at the end of treatment. Compared with MRD-positive, MRD-negative status with CR/CRi was associated with significantly improved overall survival and progression-free survival, respectively: hazard ratio (97.5% confidence interval; one-sided P-value) 0.512 (97.5% CI [0.313-0.835]; P = 0.0009) and 0.423 (97.5% CI [0.256-0.699]; P < 0.0001). Median overall survival was 14.1 versus 7.2 months, in the MRD-negative versus MRD-positive groups. Patients in first salvage who achieved MRD negativity at the end of treatment experienced significantly improved survival versus that seen in MRD-positive patients, particularly for those patients who proceeded to stem cell transplant. Among patients with relapsed/refractory acute lymphocytic leukemia who received inotuzumab, those with MRD-negative CR/CRi had the best survival outcomes.

Randomized comparison of low dose cytarabine with or without glasdegib in patients with newly diagnosed acute myeloid leukemia or high-risk myelodysplastic syndrome.

Glasdegib is a Hedgehog pathway inhibitor. This phase II, randomized, open-label, multicenter study (ClinicalTrials.gov, NCT01546038) evaluated the efficacy of glasdegib plus low-dose cytarabine (LDAC) in patients with acute myeloid leukemia (AML) or high-risk myelodysplastic syndrome unsuitable for intensive chemotherapy. Glasdegib 100 mg (oral, QD) was administered continuously in 28-day cycles; LDAC 20 mg (subcutaneous, BID) was administered for 10 per 28 days. Patients (stratified by cytogenetic risk) were randomized (2:1) to receive glasdegib/LDAC or LDAC. The primary endpoint was overall survival. Eighty-eight and 44 patients were randomized to glasdegib/LDAC and LDAC, respectively. Median (80% confidence interval [CI]) overall survival was 8.8 (6.9-9.9) months with glasdegib/LDAC and 4.9 (3.5-6.0) months with LDAC (hazard ratio, 0.51; 80% CI, 0.39-0.67, P = 0.0004). Fifteen (17.0%) and 1 (2.3%) patients in the glasdegib/LDAC and LDAC arms, respectively, achieved complete remission (P < 0.05). Nonhematologic grade 3/4 all-causality adverse events included pneumonia (16.7%) and fatigue (14.3%) with glasdegib/LDAC and pneumonia (14.6%) with LDAC. Clinical efficacy was evident across patients with diverse mutational profiles. Glasdegib plus LDAC has a favorable benefit-risk profile and may be a promising option for AML patients unsuitable for intensive chemotherapy.

Inhibition of the T790M gatekeeper mutant of the epidermal growth factor receptor by EXEL-7647.

PURPOSE: Agents inhibiting the epidermal growth factor receptor (EGFR) have shown clinical benefit in a subset of non-small cell lung cancer patients expressing amplified or mutationally activated EGFR. However, responsive patients can relapse as a result of selection for EGFR gene mutations that confer resistance to ATP competitive EGFR inhibitors, such as erlotinib and gefitinib. We describe here the activity of EXEL-7647 (XL647), a novel spectrum-selective kinase inhibitor with potent activity against the EGF and vascular endothelial growth factor receptor tyrosine kinase families, against both wild-type (WT) and mutant EGFR in vitro and in vivo. EXPERIMENTAL DESIGN: The activity of EGFR inhibitors against WT and mutant EGFRs and their effect on downstream signal transduction was examined in cellular assays and in vivo using A431 and MDA-MB-231 (WT EGFR) and H1975 (L858R and T790M mutant EGFR) xenograft tumors. RESULTS: EXEL-7647 shows potent and long-lived inhibition of the WT EGFR in vivo. In addition, EXEL-7647 inhibits cellular proliferation and EGFR pathway activation in the erlotinib-resistant H1975 cell line that harbors a double mutation (L858R and T790M) in the EGFR gene. In vivo efficacy studies show that EXEL-7647 substantially inhibited the growth of H1975 xenograft tumors and reduced both tumor EGFR signaling and tumor vessel density. Additionally, EXEL-7647, in contrast to erlotinib, substantially inhibited the growth and vascularization of MDA-MB-231 xenografts, a model which is more reliant on signaling through vascular endothelial growth factor receptors. CONCLUSIONS: These studies provide a preclinical basis for clinical trials of XL647 in solid tumors and in patients bearing tumors that are resistant to existing EGFR-targeted therapies.

Phase Ib Study of Glasdegib, a Hedgehog Pathway Inhibitor, in Combination with Standard Chemotherapy in Patients with AML or High-Risk MDS.

Purpose: This open-label, multicenter, dose-finding, phase Ib study (NCT01546038) evaluated the safety, pharmacokinetics, pharmacodynamics, and clinical activity of the novel Hedgehog pathway Smoothened inhibitor glasdegib (PF-04449913) in patients (N = 52) with acute myeloid leukemia (AML) or high-risk myelodysplastic syndrome (MDS).Experimental Design: Glasdegib 100 or 200 mg was administered orally, once daily in 28-day cycles, in combination with low-dose cytarabine (arm A) or decitabine (arm B) to newly diagnosed patients considered not suitable for standard induction chemotherapy, and in combination with cytarabine/daunorubicin (arm C) to fit patients. The study followed a standard 3+3 dose-escalation design. The primary endpoint was dose-limiting toxicity (DLT). Ten additional patients were enrolled in expansion cohorts of arms A (n = 23) and C (n = 22) to confirm the recommended phase II dose (RP2D).Results: No DLTs were observed in arms A and B; 1 DLT (grade 4 neuropathy) occurred in arm C. The most common treatment-related nonhematologic adverse events were mostly grades 1 and 2 in all arms. Muscle spasms, dysgeusia, and alopecia were generally mild. Overall, 16 patients (31%) achieved a complete remission (CR)/CR with incomplete blood count recovery. Note that 100 mg daily was selected as the RP2D for glasdegib in combination with standard chemotherapies in the absence of an estimated MTD in this setting.Conclusions: Treatment with glasdegib in combination with standard chemotherapy was generally well-tolerated and consistent with prior findings, warranting further evaluation of glasdegib-based combinations in patients with AML or high-risk MDS. Clin Cancer Res; 24(10); 2294-303. ©2018 AACR.

Contribution of individual targets to the antitumor efficacy of the multitargeted receptor tyrosine kinase inhibitor SU11248.

Recent achievements in the development of multitargeted molecular inhibitors necessitate a better understanding of the contribution of activity against individual targets to their efficacy. SU11248, a small-molecule inhibitor targeting class III/V receptor tyrosine kinases, including the platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF) receptors, KIT and FLT3, exhibits direct effects on cancer cells as well as antiangiogenic activity. Here, we investigated the contributions of inhibiting individual SU11248 target receptors to its overall antitumor efficacy in tumor models representing diverse signaling paradigms. Consistent with previous results, SU11248 was highly efficacious (frequently cytoreductive) in all models tested. To elucidate the specific contributions of inhibition of PDGF and VEGF receptors to the in vivo efficacy of SU11248, we employed two selective inhibitors, SU10944 (VEGF receptor inhibitor) and Gleevec (PDGF receptor inhibitor). SU10944 alone induced a tumor growth delay in all models evaluated, consistent with a primarily antiangiogenic mode of action. In contrast, Gleevec resulted in modest growth inhibition in tumor models in which the cancer cells expressed its targets (PDGFRbeta and KIT), but was not efficacious against tumors not driven by these target receptor tyrosine kinases. Strikingly, in all but one tumor model evaluated, the antitumor efficacy of SU10944 combined with Gleevec was similar to that of single-agent SU11248, and was greatly superior to that of each compound alone, indicating that the antitumor potency of SU11248 in these models stems from combined inhibition of both PDGF and VEGF receptors. The one exception was a model driven by an activated mutant of FLT3, in which the activity of SU11248, which targets FLT3, was greater than that of SU10944 plus Gleevec. Moreover, SU10944 combined with Gleevec inhibited tumor neoangiogenesis to an extent comparable to that of SU11248. Thus, the potent efficacy of SU11248 in models representing diverse signaling paradigms results from simultaneous inhibition of individual target receptors expressed both in cancer cells and in the tumor neovasculature, supporting the hypothesis that multitargeted inhibitors have the cumulative antitumor efficacy of combined single-target inhibitors.

SU14813: a novel multiple receptor tyrosine kinase inhibitor with potent antiangiogenic and antitumor activity.

Receptor tyrosine kinases (RTK), such as vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor (PDGFR), stem cell factor receptor (KIT), and fms-like tyrosine kinase 3 (FLT3), are expressed in malignant tissues and act in concert, playing diverse and major roles in angiogenesis, tumor growth, and metastasis. With the exception of a few malignancies, seemingly driven by a single genetic mutation in a signaling protein, most tumors are the product of multiple mutations in multiple aberrant signaling pathways. Consequently, simultaneous targeted inhibition of multiple signaling pathways could be more effective than inhibiting a single pathway in cancer therapies. Such a multitargeted strategy has recently been validated in a number of preclinical and clinical studies using RTK inhibitors with broad target selectivity. SU14813, a small molecule identified from the same chemical library used to isolate sunitinib, has broad-spectrum RTK inhibitory activity through binding to and inhibition of VEGFR, PDGFR, KIT, and FLT3. In cellular assays, SU14813 inhibited ligand-dependent and ligand-independent proliferation, migration, and survival of endothelial cells and/or tumor cells expressing these targets. SU14813 inhibited VEGFR-2, PDGFR-beta, and FLT3 phosphorylation in xenograft tumors in a dose- and time-dependent fashion. The plasma concentration required for in vivo target inhibition was estimated to be 100 to 200 ng/mL. Used as monotherapy, SU14813 exhibited broad and potent antitumor activity resulting in regression, growth arrest, or substantially reduced growth of various established xenografts derived from human or rat tumor cell lines. Treatment in combination with docetaxel significantly enhanced both the inhibition of primary tumor growth and the survival of the tumor-bearing mice compared with administration of either agent alone. In summary, SU14813 inhibited target RTK activity in vivo in association with reduction in angiogenesis, target RTK-mediated proliferation, and survival of tumor cells, leading to broad and potent antitumor efficacy. These data support the ongoing phase I clinical evaluation of SU14813 in advanced malignancies.