Nirogacestat, a γ-Secretase Inhibitor for Desmoid Tumors.

BACKGROUND: Desmoid tumors are rare, locally aggressive, highly recurrent soft-tissue tumors without approved treatments. METHODS: We conducted a phase 3, international, double-blind, randomized, placebo-controlled trial of nirogacestat in adults with progressing desmoid tumors according to the Response Evaluation Criteria in Solid Tumors, version 1.1. Patients were assigned in a 1:1 ratio to receive the oral γ-secretase inhibitor nirogacestat (150 mg) or placebo twice daily. The primary end point was progression-free survival. RESULTS: From May 2019 through August 2020, a total of 70 patients were assigned to receive nirogacestat and 72 to receive placebo. Nirogacestat had a significant progression-free survival benefit over placebo (hazard ratio for disease progression or death, 0.29; 95% confidence interval, 0.15 to 0.55; P<0.001); the likelihood of being event-free at 2 years was 76% with nirogacestat and 44% with placebo. Between-group differences in progression-free survival were consistent across prespecified subgroups. The percentage of patients who had an objective response was significantly higher with nirogacestat than with placebo (41% vs. 8%; P<0.001), with a median time to response of 5.6 months and 11.1 months, respectively; the percentage of patients with a complete response was 7% and 0%, respectively. Significant between-group differences in secondary patient-reported outcomes, including pain, symptom burden, physical or role functioning, and health-related quality of life, were observed (P≤0.01). Frequent adverse events with nirogacestat included diarrhea (in 84% of the patients), nausea (in 54%), fatigue (in 51%), hypophosphatemia (in 42%), and maculopapular rash (in 32%); 95% of adverse events were of grade 1 or 2. Among women of childbearing potential receiving nirogacestat, 27 of 36 (75%) had adverse events consistent with ovarian dysfunction, which resolved in 20 women (74%). CONCLUSIONS: Nirogacestat was associated with significant benefits with respect to progression-free survival, objective response, pain, symptom burden, physical functioning, role functioning, and health-related quality of life in adults with progressing desmoid tumors. Adverse events with nirogacestat were frequent but mostly low grade. (Funded by SpringWorks Therapeutics; DeFi ClinicalTrials.gov number, NCT03785964.).

Larotrectinib efficacy and safety in adult patients with tropomyosin receptor kinase fusion sarcomas.

BACKGROUND: Larotrectinib, a first-in-class, highly selective tropomyosin receptor kinase (TRK) inhibitor, has demonstrated efficacy in adult and pediatric patients with various solid tumors harboring NTRK gene fusions. This subset analysis focuses on the efficacy and safety of larotrectinib in an expanded cohort of adult patients with TRK fusion sarcomas. METHODS: Patients (≥18 years old) with sarcomas harboring NTRK gene fusions were identified from three clinical trials. Patients received larotrectinib 100 mg orally twice daily. Response was investigator-assessed per RECIST v1.1. Data cutoff was July 20, 2021. RESULTS: At the data cutoff, 36 adult patients with TRK fusion sarcomas had initiated larotrectinib therapy: two (6%) patients had bone sarcomas, four (11%) had gastrointestinal stromal tumors, and 30 (83%) had soft tissue sarcomas. All patients were evaluable for response and demonstrated an objective response rate of 58% (95% confidence interval, 41-74). Patients responded well to larotrectinib regardless of number of prior lines of therapy. Adverse events (AEs) were mostly grade 1/2. Grade 3 treatment-emergent AEs (TEAEs) occurred in 15 (42%) patients. There were no grade 4 TEAEs. Two grade 5 TEAEs were reported, neither of which were considered related to larotrectinib. Four (11%) patients permanently discontinued treatment due to TEAEs. CONCLUSIONS: Larotrectinib demonstrated robust and durable responses, extended survival benefit, and a favorable safety profile in adult patients with TRK fusion sarcomas with longer follow-up. These results continue to demonstrate that testing for NTRK gene fusions should be incorporated into the clinical management of adult patients with various types of sarcomas. PLAIN LANGUAGE SUMMARY: Tropomyosin receptor kinase (TRK) fusion proteins result from translocations involving the NTRK gene and cause cancer in a range of tumor types. Larotrectinib is an agent that specifically targets TRK fusion proteins and is approved for the treatment of patients with TRK fusion cancer. This study looked at how well larotrectinib worked in adult patients with sarcomas caused by TRK fusion proteins. Over half of patients had a durable response to larotrectinib, with no unexpected side effects. These results show that larotrectinib is safe and effective in adult patients with TRK fusion sarcomas.

Combining Poly (ADP-Ribose) Polymerase (PARP) Inhibitors with Chemotherapeutic Agents: Promise and Challenges.

Better understanding of molecular drivers and dysregulated pathways has furthered the concept of precision oncology and rational drug development. The role of DNA damage response (DDR) pathways has been extensively studied in carcinogenesis and as potential therapeutic targets to improve response to chemotherapy or overcome resistance. Treatment with small molecule inhibitors of PARP has resulted in clinical response and conferred survival benefit to patients with ovarian cancer, BRCA-mutant breast cancer, HRD-deficient prostate cancer and BRCA-mutant pancreatic cancer, leading to US Food and Drug Administration (FDA) approvals. However, the observed clinical benefit with single agent PARP inhibitors is limited to few tumor types within the relevant genetic context. Since DDR pathways are essential for repair of damage caused by cytotoxic agents, PARP inhibitors have been evaluated in combination with various chemotherapeutic agents to broaden the therapeutic application of this class of drugs. In this chapter, we discuss the combination of PARP inhibitors with different chemotherapeutics agents, clinical experience to date, lessons learnt, and future directions for this approach.

Efficacy of Larotrectinib in TRK Fusion-Positive Cancers in Adults and Children.

BACKGROUND: Fusions involving one of three tropomyosin receptor kinases (TRK) occur in diverse cancers in children and adults. We evaluated the efficacy and safety of larotrectinib, a highly selective TRK inhibitor, in adults and children who had tumors with these fusions. METHODS: We enrolled patients with consecutively and prospectively identified TRK fusion-positive cancers, detected by molecular profiling as routinely performed at each site, into one of three protocols: a phase 1 study involving adults, a phase 1-2 study involving children, or a phase 2 study involving adolescents and adults. The primary end point for the combined analysis was the overall response rate according to independent review. Secondary end points included duration of response, progression-free survival, and safety. RESULTS: A total of 55 patients, ranging in age from 4 months to 76 years, were enrolled and treated. Patients had 17 unique TRK fusion-positive tumor types. The overall response rate was 75% (95% confidence interval [CI], 61 to 85) according to independent review and 80% (95% CI, 67 to 90) according to investigator assessment. At 1 year, 71% of the responses were ongoing and 55% of the patients remained progression-free. The median duration of response and progression-free survival had not been reached. At a median follow-up of 9.4 months, 86% of the patients with a response (38 of 44 patients) were continuing treatment or had undergone surgery that was intended to be curative. Adverse events were predominantly of grade 1, and no adverse event of grade 3 or 4 that was considered by the investigators to be related to larotrectinib occurred in more than 5% of patients. No patient discontinued larotrectinib owing to drug-related adverse events. CONCLUSIONS: Larotrectinib had marked and durable antitumor activity in patients with TRK fusion-positive cancer, regardless of the age of the patient or of the tumor type. (Funded by Loxo Oncology and others; ClinicalTrials.gov numbers, NCT02122913 , NCT02637687 , and NCT02576431 .).

Combination therapy with pazopanib and tivantinib modulates VEGF and c-MET levels in refractory advanced solid tumors.

The vascular endothelial growth factor (VEGF)/VEGFR and hepatocyte growth factor (HGF)/c-MET signaling pathways act synergistically to promote angiogenesis. Studies indicate VEGF inhibition leads to increased levels of phosphorylated c-MET, bypassing VEGF-mediated angiogenesis and leading to chemoresistance. We conducted a phase 1 clinical trial with 32 patients with refractory solid tumors to evaluate the safety, pharmacokinetics, and pharmacodynamics of combinations of VEGF-targeting pazopanib and the putative c-MET inhibitor ARQ197 (tivantinib) at 5 dose levels (DLs). Patients either took pazopanib and tivantinib from treatment initiation (escalation phase) or pazopanib alone for 7 days, with paired tumor sampling, prior to starting combination treatment (expansion phase). Hypertension was the most common adverse event. No more than 1 dose limiting toxicity (DLT) occurred at any DL, so the maximum tolerated dose (MTD) was not determined; DL5 (800 mg pazopanib daily and 360 mg tivantinib BID) was used during the expansion phase. Twenty of 31 evaluable patients achieved stable disease lasting up to 22 cycles. Circulating VEGF, VEGFR2, HGF, and c-MET levels were assessed, and only VEGF levels increased. Tumor c-MET levels (total and phosphorylated) were determined in paired biopsies before and after 7 days of pazopanib treatment. Total intact c-MET decreased in 6 of 7 biopsy pairs, in contrast to previously reported c-MET elevation in response to VEGF inhibition. These results are discussed in the context of our previously reported analysis of epithelial-mesenchymal transition in these tumors.

Larotrectinib in patients with TRK fusion-positive solid tumours: a pooled analysis of three phase 1/2 clinical trials.

BACKGROUND: The selective TRK inhibitor larotrectinib was approved for paediatric and adult patients with advanced TRK fusion-positive solid tumours based on a primary analysis set of 55 patients. The aim of our analysis was to explore the efficacy and long-term safety of larotrectinib in a larger population of patients with TRK fusion-positive solid tumours. METHODS: Patients were enrolled and treated in a phase 1 adult, a phase 1/2 paediatric, or a phase 2 adolescent and adult trial. Some eligibility criteria differed between these studies. For this pooled analysis, eligible patients were aged 1 month or older, with a locally advanced or metastatic non-CNS primary, TRK fusion-positive solid tumour, who had received standard therapy previously if available. This analysis set includes the 55 patients on which approval of larotrectinib was based. Larotrectinib was administered orally (capsule or liquid formulation), on a continuous 28-day schedule, to adults mostly at a dose of 100 mg twice daily, and to paediatric patients mostly at a dose of 100 mg/m2 (maximum of 100 mg) twice daily. The primary endpoint was objective response as assessed by local investigators in an intention-to-treat analysis. Contributing trials are registered with ClinicalTrials.gov, NCT02122913 (active not recruiting), NCT02637687 (recruiting), and NCT02576431 (recruiting). FINDINGS: Between May 1, 2014, and Feb 19, 2019, 159 patients with TRK fusion-positive cancer were enrolled and treated with larotrectinib. Ages ranged from less than 1 month to 84 years. The proportion of patients with an objective response according to investigator assessment was 121 (79%, 95% CI 72-85) of 153 evaluable patients, with 24 (16%) having complete responses. In a safety population of 260 patients treated regardless of TRK fusion status, the most common grade 3 or 4 larotrectinib-related adverse events were increased alanine aminotransferase (eight [3%] of 260 patients), anaemia (six, 2%), and decreased neutrophil count (five [2%]). The most common larotrectinib-related serious adverse events were increased alanine aminotransferase (two [<1%] of 260 patients), increased aspartate aminotransferase (two [<1%]), and nausea (two [<1%]). No treatment-related deaths occurred. INTERPRETATION: These data confirm that TRK fusions define a unique molecular subgroup of advanced solid tumours for which larotrectinib is highly active. Safety data indicate that long-term administration of larotrectinib is feasible. FUNDING: Bayer and Loxo Oncology.

A phase I pharmacokinetic study of belinostat in patients with advanced cancers and varying degrees of liver dysfunction.

AIMS: The histone deacetylase inhibitor belinostat has activity in various cancers. Because belinostat is metabolized by the liver, reduced hepatic clearance could lead to excessive drug accumulation and increased toxicity. Safety data in patients with liver dysfunction are needed for this drug to reach its full potential in the clinic. METHODS: We performed a phase 1 trial to determine the safety, maximum tolerated dose (MTD) and pharmacokinetics of belinostat in patients with advanced cancer and varying degrees of liver dysfunction. RESULTS: Seventy-two patients were enrolled and divided into cohorts based on liver function. In patients with mild dysfunction, the MTD was the same as the recommended phase 2 dose (1000 mg/m2 /day). Belinostat was well tolerated in patients with moderate and severe liver dysfunction, although the trial was closed before the MTD in these cohorts could be determined. The mean clearance of belinostat was 661 mL/min/m2 in patients with normal liver function, compared to 542, 505 and 444 mL/min/m2 in patients with mild, moderate and severe hepatic dysfunction. Although this trial was not designed to assess clinical activity, of the 47 patients evaluable for response, 13 patients (28%) experienced stable disease. CONCLUSION: While a statistically significant difference in clearance indicates increased belinostat exposure with worsening liver function, no relationship was observed between belinostat exposure and toxicity. An assessment of belinostat metabolites revealed significant differences in metabolic pathway capability in patients with differing levels of liver dysfunction. Further studies are needed to establish formal dosing guidelines in this patient population.

Cediranib phase-II study in children with metastatic alveolar soft-part sarcoma (ASPS).

BACKGROUND: Alveolar soft-part sarcoma (ASPS), a rare vascular sarcoma with a clinically indolent course, frequently presents with metastases. Vascular endothelial growth factor (VEGF) is a promising therapeutic target. In a phase-II trial of the VEGF receptor inhibitor cediranib for adults with ASPS, the partial response (PR) rate (response evaluation criteria in solid tumors [RECIST] v1.0) was 35% (15/43; 95% confidence interval: 21-51%). We evaluated cediranib in the pediatric population. PROCEDURE: Patients <16 years old with metastatic, unresectable ASPS received cediranib at the pediatric maximum tolerated dose of 12 mg/m2 (≈70% of the fixed adult phase-II dose orally daily). Tumor response was assessed every two cycles (RECIST v1.0). A Simon two-stage optimal design (target response rate 35%, rule out 5%) was used. RESULTS: Seven patients (four females), with a median age of 13 years, (range 9-15), were enrolled on stage 1. The most frequent grade 2 or 3 adverse events were neutropenia, diarrhea, hypertension, fatigue, and proteinuria. The best response was stable disease (SD) (median cycle number = 34). Three patients were removed from the study treatment for disease progression (cycles 4, 5, and 36). Five of seven patients had SD for ≥14 months. Two patients with SD remain on study (34-57+ cycles). CONCLUSIONS: Cediranib did not reach the target response rate in this small pediatric cohort, in contrast to the adult 35% PR rate. The pediatric dosing was 30% lower compared to the adult dosing, which may have contributed to response differences. Prolonged SD was observed in five patients, but given the indolent nature of ASPS, SD cannot be clearly attributed to cediranib. Cediranib has an acceptable safety profile.

A Phase I Study of Ganetespib and Ziv-Aflibercept in Patients with Advanced Carcinomas and Sarcomas.

LESSONS LEARNED: The combination of the antiangiogenic agent ziv-aflibercept and the heat shock protein 90 inhibitor ganetespib was associated with several serious and unexpected adverse events and was not tolerable on the dosing schedule tested.Studies such as these emphasize the importance of considering overlapping toxicities when designing novel treatment combination regimens. BACKGROUND: Although inhibition of angiogenesis is an effective strategy for cancer treatment, acquired resistance to antiangiogenic therapy is common. Heat shock protein 90 (Hsp90) is a molecular chaperone that regulates various oncogenic signaling pathways involved in acquired resistance and has been shown to play a role in angiogenesis. Combining an antiangiogenic agent with an Hsp90 inhibitor has therefore been proposed as a strategy for preventing resistance and improving antitumor activity. We conducted a single-arm phase I study evaluating the combination of ziv-aflibercept, an antiangiogenic drug, with the Hsp90 inhibitor ganetespib. METHODS: Adult patients were eligible if they had recurrent or metastatic gastrointestinal carcinomas, nonsquamous non-small cell lung carcinomas, urothelial carcinomas, or sarcomas that had progressed after at least one line of standard therapy. Ziv-aflibercept was administered intravenously on days 1 and 15, and ganetespib was administered intravenously on days 1, 8, and 15, of each 28-day cycle. RESULTS: Five patients were treated with the combination. Although three patients achieved stable disease, study treatment was associated with several serious and unexpected adverse events. CONCLUSION: The dose escalation phase of this study was not completed, but the limited data obtained suggest that this combination may be too toxic when administered on this dosing schedule.

Reviewing the role of healthy volunteer studies in drug development.

BACKGROUND: With the exception of genotoxic oncology drugs, first-in-human, Phase 1 clinical studies of investigational drugs have traditionally been conducted in healthy volunteers (HVs). The primary goal of these studies is to investigate the pharmacokinetics and pharmacodynamics of a novel drug candidate, determine appropriate dosing, and document safety and tolerability. MAIN BODY: When tailored to specific study objectives, HV studies are beneficial to manufacturers and patients alike and can be applied to both non-oncology and oncology drug development. Enrollment of HVs not only increases study accrual rates for dose-escalation studies but also alleviates the ethical concern of enrolling patients with disease in a short-term study at subtherapeutic doses when other studies (e.g. Phase 2 or Phase 3 studies) may be more appropriate for the patient. The use of HVs in non-oncology Phase 1 clinical trials is relatively safe but nonetheless poses ethical challenges because of the potential risks to which HVs are exposed. In general, most adverse events associated with non-oncology drugs are mild in severity, and serious adverse events are rare, but examples of severe toxicity have been reported. The use of HVs in the clinical development of oncology drugs is more limited but is nonetheless useful for evaluating clinical pharmacology and establishing an appropriate starting dose for studies in cancer patients. During the development of oncology drugs, clinical pharmacology studies in HVs have been used to assess pharmacokinetics, drug metabolism, food effects, potential drug-drug interactions, effects of hepatic and renal impairment, and other pharmacologic parameters vital for clinical decision-making in oncology. Studies in HVs are also being used to evaluate biosimilars versus established anticancer biologic agents. CONCLUSION: A thorough assessment of toxicity and pharmacology throughout the drug development process is critical to ensure the safety of HVs. With the appropriate safeguards, HVs will continue to play an important role in future drug development.

First-in-human study of the epichaperome inhibitor PU-H71: clinical results and metabolic profile.

Background Molecular chaperone targeting has shown promise as a therapeutic approach in human cancers of various histologies and genetic backgrounds. The purine-scaffold inhibitor PU-H71 (NSC 750424), selective for Hsp90 in epichaperome networks, has demonstrated antitumor activity in multiple preclinical cancer models. The present study was a first in-human trial of PU-H71 aimed at establishing its safety and tolerability and characterizing its pharmacokinetic (PK) profile on a weekly administration schedule in human subjects with solid tumors refractory to standard treatments. Methods PU-H71 was administered intravenously over 1 h on days 1 and 8 of 21-day cycles in patients with refractory solid tumors. Dose escalation followed a modified accelerated design. Blood and urine were collected during cycles 1 and 2 for pharmacokinetics analysis. Results Seventeen patients were enrolled in this trial. Grade 2 and 3 adverse events were observed but no dose limiting toxicities occurred, thus the human maximum tolerated dose was not determined. The mean terminal half-life (T1/2) was 8.4 ± 3.6 h, with no dependency to dose level. A pathway for the metabolic disposal of PU-H71 in humans was derived from microsome studies. Fourteen patients were also evaluable for clinical response; 6 (35%) achieved a best response of stable disease for >2 cycles, with 2 patients remaining on study for 6 cycles. The study closed prematurely due to discontinuation of drug supply. Conclusions PU-H71 was well tolerated at the doses administered during this study (10 to 470 mg/m2/day), with no dose limiting toxicities.

Biologic and clinical characteristics of adolescent and young adult cancers: Acute lymphoblastic leukemia, colorectal cancer, breast cancer, melanoma, and sarcoma.

Adolescent and young adult (AYA) patients with cancer have not attained the same improvements in overall survival as either younger children or older adults. One possible reason for this disparity may be that the AYA cancers exhibit unique biologic characteristics, resulting in differences in clinical and treatment resistance behaviors. This report from the biologic component of the jointly sponsored National Cancer Institute and LiveStrong Foundation workshop entitled "Next Steps in Adolescent and Young Adult Oncology" summarizes the current status of biologic and translational research progress for 5 AYA cancers; colorectal cancer breast cancer, acute lymphoblastic leukemia, melanoma, and sarcoma. Conclusions from this meeting included the need for basic biologic, genomic, and model development for AYA cancers as well as translational research studies to elucidate any fundamental differences between pediatric, AYA, and adult cancers. The biologic questions for future research are whether there are mutational or signaling pathway differences (for example, between adult and AYA colorectal cancer) that can be clinically exploited to develop novel therapies for treating AYA cancers and to develop companion diagnostics.

Randomized phase II trial of cyclophosphamide and the oral poly (ADP-ribose) polymerase inhibitor veliparib in patients with recurrent, advanced triple-negative breast cancer.

Background In tumors carrying BRCA mutations, DNA damage caused by standard cytotoxic chemotherapy can be potentiated by poly [ADP-ribose] polymerase (PARP) inhibitors, leading to increased cell death through synthetic lethality. Individuals carrying mutations in BRCA have an increased incidence of triple negative breast cancer (TNBC). In order to assess the role of PARP inhibition in the treatment of TNBC, we conducted a randomized phase II trial of the combination of veliparib, a small molecule PARP inhibitor, with the cytotoxic agent cyclophosphamide versus cyclophosphamide alone in patients with refractory TNBC. Methods Adult patients with TNBC were randomized to receive oral cyclophosphamide 50 mg once daily with or without oral veliparib at 60 mg daily in 21-day cycles. Patients on the cyclophosphamide arm could crossover to the combination arm at disease progression. Results Forty-five patients were enrolled; 18 received cyclophosphamide alone and 21 received the combination as their initial treatment regimen. Lymphopenia was the most common grade 3/4 toxicity noted in both arms. One patient in the cyclophosphamide alone arm, and 2 in the combination arm had objective responses. Response rates and median progression free survival did not significantly differ between both treatment arms. Conclusion The addition of veliparib to cyclophosphamide, at the dose and schedule evaluated, did not improve the response rate over cyclophosphamide treatment alone in patients with heavily pre-treated triple-negative breast cancer.

Compressing drug development timelines in oncology using phase '0' trials.

The optimal evaluation of molecularly targeted anticancer agents requires the integration of pharmacodynamic assays into early clinical investigations. Phase '0' trials conducted under the new Exploratory Investigational New Drug Guidance from the US Food and Drug Administration can provide a platform to establish the feasibility of assays for target modulation in human samples, evaluate biomarkers for drug effects and provide pharmacokinetic data. Phase 0 trials could facilitate rational drug selection, identify therapeutic failures early, and might compress timelines for anticancer drug development. We expect that such trials will become a routine part of early-phase oncological drug development in the future.

Delivering on the promise: poly ADP ribose polymerase inhibition as targeted anticancer therapy.

PURPOSE OF REVIEW: The article presents the rationale, clinical development, and current status of poly (ADP ribose) polymerase inhibitors (PARPis) as anticancer agents. RECENT FINDINGS: The recent approval of olaparib in heavily pretreated patients with advanced ovarian cancer carrying a BRCA1/2 mutation represents a significant therapeutic advance for patients with this difficult to treat disease. Though olaparib is the first agent in this class to be approved, multiple PARPis are in various stages of clinical development, including in combination with other treatment modalities such as radiation, antiangiogenic agents, and cytotoxic chemotherapies. SUMMARY: Clinical benefit has been observed with PARPis in patients with advanced BRCA1/2 mutant ovarian and breast cancers. Various PARPis, either as single agents or in combination, are being evaluated in the neoadjuvant, adjuvant, and metastatic settings.

Biomarker-driven phase 2 study of MK-2206 and selumetinib (AZD6244, ARRY-142886) in patients with colorectal cancer.

PURPOSE: PI3K/AKT/mTOR and RAS/RAF/MEK pathways are frequently dysregulated in colorectal cancer (CRC). We conducted a biomarker-driven trial of the combination of MK-2206, an allosteric AKT 1/2/3 inhibitor, and selumetinib, a MEK 1/2 inhibitor, in patients with CRC to evaluate inhibition of phosphorylated ERK (pERK) and AKT (pAKT) in paired tumor biopsies. PATIENTS AND METHODS: Adult patients with advanced CRC were enrolled in successive cohorts stratified by KRAS mutation status. Initially, 12 patients received oral MK-2206 90 mg weekly with oral selumetinib 75 mg daily in 28-day cycles. Following an interim analysis, the doses of MK-2206 and selumetinib were increased to 135 mg weekly and 100 mg daily, respectively. Paired tumor biopsies were evaluated for target modulation. RESULTS: Common toxicities were gastrointestinal, hepatic, dermatologic, and hematologic. Of 21 patients enrolled, there were no objective responses. Target modulation did not achieve the pre-specified criteria of dual 70 % inhibition of pERK and pAKT levels in paired tumor biopsies. CONCLUSION: Despite strong scientific rationale and preclinical data, clinical activity was not observed. The desired level of target inhibition was not achieved. Overlapping toxicities limited the ability to dose escalate to achieve exposures likely needed for clinical activity, highlighting the challenges in developing optimal combinations of targeted agents.

Phase I study of the heat shock protein 90 (Hsp90) inhibitor onalespib (AT13387) administered on a daily for 2 consecutive days per week dosing schedule in patients with advanced solid tumors.

Inhibition of heat shock 90 (Hsp90) molecular chaperones allows targeting of multiple proteins involved in tumorigenesis. We investigated the safety, recommended phase 2 dose (RP2D), and pharmacokinetic and pharmacodynamic profile of onalespib (AT13387), a potent synthetic Hsp90 inhibitor, administered on days 1, 2, 8, 9, 15, and 16 of 28 day cycles (QDx2/week) in a phase I trial. This study followed an accelerated titration design with a starting dose of 20 mg/m(2)/dose and a standard 3 + 3 dose escalation design for dose level 4 (120 mg/m(2)/dose) and above. Additional patients were enrolled at the RP2D with mandatory paired tumor biopsies to assess modulation of 210 client proteins using reverse phase protein array analysis. Thirty-one patients were treated; RP2D was established at 160 mg/m(2)/dose on the QDx2/week schedule. Common toxicities were gastrointestinal, hepatic, and hematologic. Pharmacokinetic profile was linear and plasma levels increased proportionally with dose (T½ ~8 h). No responses were observed; eight patients had stable disease for > 2 cycles with one patient remaining on study for 6 cycles. Target engagement was demonstrated by transcriptional upregulation of Hsp70 and Hsp27 in PBMCs. Statistically significant modulation of client proteins was not achieved in the 9 paired tumor biopsies evaluated; however, hierarchical clustering revealed two subgroups of patients with differential patterns of protein expression. Further combination studies are needed in order to target prospective driver oncoproteins.

Weekly EZN-2208 (PEGylated SN-38) in combination with bevacizumab in patients with refractory solid tumors.

BACKGROUND: Anti-angiogenic therapies such as bevacizumab upregulate hypoxia-inducible factor-1α (HIF-1α), a possible mechanism of drug resistance. Camptothecin analogues, including SN-38, have been shown to reduce the expression and transcriptional activity of HIF-1α in preclinical models. We hypothesized that co-administration of pegylated SN-38 (EZN-2208) may offset the induction of HIF-1α following bevacizumab treatment, resulting in synergistic antitumor effects. PATIENTS AND METHODS: Patients with refractory solid tumors were enrolled. Objectives were to evaluate the modulation of HIF-1α protein and target genes in tumor biopsies following administration of the combination of EZN-2208 administered weekly × 3 (days 1, 8, 15) and bevacizumab administered every 2 weeks, in 28-day cycles, and to establish the safety and tolerability of the combination. Tumor biopsies and dynamic contrast enhanced MRI (DCE-MRI) were obtained following bevacizumab alone (before EZN-2208) and after administration of both study drugs. RESULTS: Twelve patients were enrolled; ten were evaluable for response. Prolonged stable disease was observed in 2 patients, one with HCC (16 cycles) and another with desmoplastic round cell tumor (7 cycles). Reduction in HIF-1α protein levels in tumor biopsies compared to baseline was observed in 5 of 7 patients. Quantitative analysis of DCE-MRI from 2 patients revealed changes in K(trans) and k(ep). The study closed prematurely as further clinical development of EZN-2208 was suspended by the pharmaceutical sponsor. CONCLUSION: Preliminary proof-of-concept for modulation of HIF-1α protein in tumor biopsies following administration of EZN-2208 was observed. Two of 10 patients had prolonged disease stabilization following treatment with the EZN-2208 and bevacizumab combination.

Validation of a hypoxia-inducible factor-1 alpha specimen collection procedure and quantitative enzyme-linked immunosorbent assay in solid tumor tissues.

Hypoxia-inducible factor-1 alpha (HIF-1α) is an important marker of hypoxia in human tumors and has been implicated in tumor progression. Drugs targeting HIF-1α are being developed, but the ability to measure drug-induced changes in HIF-1α is limited by the lability of the protein in normoxia. Our goal was to devise methods for specimen collection and processing that preserve HIF-1α in solid tumor tissues and to develop and validate a two-site chemiluminescent quantitative enzyme-linked immunosorbent assay (ELISA) for HIF-1α. We tested various strategies for HIF-1α stabilization in solid tumors, including nitrogen gas-purged lysis buffer, the addition of proteasome inhibitors or the prolyl hydroxylase inhibitor 2-hydroxyglutarate, and bead homogenization. Degassing and the addition of 2-hydroxyglutarate to the collection buffer significantly increased HIF-1α recovery, whereas bead homogenization in sealed tubes improved HIF-1α recovery and reduced sample variability. Validation of the ELISA demonstrated intra- and inter-assay variability of less than 15% and accuracy of 99.8±8.3% as assessed by spike recovery. Inter-laboratory reproducibility was also demonstrated (R(2)=0.999). Careful sample handling techniques allow us to quantitatively detect HIF-1α in samples as small as 2.5µg of total protein extract, and this method is currently being applied to analyze tumor biopsy specimens in early-phase clinical trials.

Illuminating immunotherapy response via precision T cell-targeted PET imaging.

Traditionally, immunotherapy agent selection and treatment strategies are guided by biopsy-based histological information. However, biopsies are limited in that they are invasive, provide static information regarding the tumor immune microenvironment, and only sample a small part of one tumor site. The tumor microenvironment is dynamic and heterogenous. As a result, the immune milieu at one site may be distinct from other metastatic sites. These factors make identifying which patients are likely to respond to different immunotherapies and which harbor intrinsic resistance mechanisms difficult to identify based on a biopsy alone. As such, there is significant interest in alternative methodologies that better characterize the tumor immune microenvironment and monitor immunotherapy response. PET imaging potentially offers a non-invasive way to characterize the tumor immune microenvironment at the primary tumor and metastases and allow for longitudinal characterization. Herein, we review pre-clinically and clinically tested T cell-targeted PET radiopharmaceuticals, as T cells have been the dominant immunotherapy target, and their utility in both evaluating response to immunotherapy and in understanding the systemic immune response to treatment with immunotherapeutics.