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Summary Over the last decade, bromodomain inhibitors have emerged as a promising class of anticancer drugs. However, the clinical progress of these agents has faced significant obstacles, which precluded their regulatory approval. This editorial will review the challenges and opportunities associated with the development of bromodomain inhibitors.

Fibroblast growth factor receptor (FGFR) 2/3 alterations have been implicated in tumorigenesis in several malignancies, including urothelial carcinoma. Several FGFR inhibitors have been studied or are in development, and erdafitinib is the sole inhibitor to achieve regulatory approval. Given the rapidly evolving treatment landscape for advanced urothelial carcinoma, including regulatory approvals and withdrawals, determining the most appropriate treatment strategies and sequencing for FGFR-altered urothelial carcinoma is becoming increasing critical. However, the clinical efficacy of FGFR inhibitors is limited by acquired resistance similar to that seen with other tyrosine kinase inhibitors. Additional challenges to the clinical use of FGFR inhibitors include treatment-related adverse events and the financial costs associated with treatment. In this review, we describe known mechanisms of FGFR inhibitor resistance, including gatekeeper mutations, domain mutations, and the development of new mutations. In addition, we discuss management strategies, including ongoing clinical trials evaluating FGFR inhibitors, antibody-drug conjugates, and combination therapies with immune checkpoint inhibitors that may provide additional treatment options for localized and metastatic urothelial carcinoma.

Autophagy is an evolutionarily conserved cell survival pathway that enables cells to recoup ATP and other critical biosynthetic molecules during nutrient deprivation or exposure to hypoxia, which are hallmarks of the tumour microenvironment. Autophagy has been implicated as a potential mechanism of resistance to anticancer agents as it can promote cell survival in the face of stress induced by chemotherapeutic agents by breaking down cellular components to generate alternative sources of energy. Disruption of autophagy with chloroquine (CQ) induces the accumulation of ubiquitin‐conjugated proteins in a manner similar to the proteasome inhibitor bortezomib (BZ). However, CQ‐induced protein accumulation occurs at a slower rate and is localized to lysosomes in contrast to BZ, which stimulates rapid buildup of ubiquitinated proteins and aggresome formation in the cytosol. The histone deacetylase (HDAC) inhibitor vorinostat (VOR) blocked BZ‐induced aggresome formation, but promoted CQ‐mediated ubiquitinated protein accumulation. Disruption of autophagy with CQ strongly enhanced VOR‐mediated apoptosis in colon cancer cells. Accordingly, knockdown of the essential autophagy gene Atg7 also sensitized cells to VOR‐induced apoptosis. Knockdown of HDAC6 greatly enhanced BZ‐induced apoptosis, but only marginally sensitized cells to CQ. Subsequent studies determined that the CQ/VOR combination promoted a large increase in superoxide generation that was required for ubiquitinated protein accumulation and cell death. Finally, treatment with the CQ/VOR combination significantly reduced tumour burden and induced apoptosis in a colon cancer xenograft model. Collectively, our results establish that inhibition of autophagy with CQ induces ubiquitinated protein accumulation and VOR potentiates CQ‐mediated aggregate formation, superoxide generation and apoptosis.

Background: Dinaciclib is a potent inhibitor of cell cycle and transcriptional cyclin-dependent kinases. This Phase 1 study evaluated the safety, tolerability and pharmacokinetics of various dosing schedules of dinaciclib in advanced solid tumour patients and assessed pharmacodynamic and preliminary anti-tumour activity. Methods: In part 1, patients were enrolled in escalating cohorts of 2-h infusions administered once every 3 weeks, utilising an accelerated titration design until a recommended phase 2 dose (RP2D) was defined. In part 2, 8- and 24-h infusions were evaluated. Pharmacokinetic parameters were determined for all schedules. Pharmacodynamic effects were assessed with an ex vivo stimulated lymphocyte proliferation assay performed in whole blood. Effects of dinaciclib on retinoblastoma (Rb) phosphorylation and other CDK targets were evaluated in skin and tumour biopsies. In addition to tumour size, metabolic response was evaluated by 18F-fluorodeoxyglucose-positron emission tomography. Results: Sixty-one patients were enrolled to parts 1 and 2. The RP2Ds were 50, 7.4 and 10.4 mg m −2 as 2- 8- and 24-hour infusions, respectively. Dose-limiting toxicities included pancytopenia, neutropenic fever, elevated transaminases, hyperuricemia and hypotension. Pharmacokinetics demonstrated rapid distribution and a short plasma half-life. Dinaciclib suppressed proliferation of stimulated lymphocytes. In skin and tumour biopsies, dinaciclib reduced Rb phosphorylation at CDK2 phospho-sites and modulated expression of cyclin D1 and p53, suggestive of CDK9 inhibition. Although there were no RECIST responses, eight patients had prolonged stable disease and received between 6 and 30 cycles. Early metabolic responses occurred. Conclusions: Dinaciclib is tolerable at doses demonstrating target engagement in surrogate and tumour tissue.

Second-generation mammalian target of rapamycin (mTOR) inhibitors such as CC-223 may have theoretical advantages over first-generation drugs by inhibiting TOR kinase in mTOR complex 1 (mTORC1) and 2 (mTORC2), potentially improving clinical efficacy for well-differentiated neuroendocrine tumors (NET).Enrolled patients had metastatic, well-differentiated NET of non-pancreatic gastrointestinal or unknown origin, with/without carcinoid symptoms, had failed ≥1 systemic chemotherapy, and were taking a somatostatin analog (SSA). Oral once-daily CC-223 was administered in 28-day cycles starting at 45 mg (n = 24), with a subsequent cohort starting at 30 mg (n = 23). Objectives were to evaluate tolerability, preliminary efficacy, and pharmacokinetic and biomarker profiles of CC-223. Forty-seven patients completed the study, with mean treatment duration of 378 days and mean dose of 26 mg; 26% of patients remained on the starting dose. Most frequent grade ≥3 toxicities were diarrhea (38%), fatigue (21%), and stomatitis (11%). By investigator, 3 of 41 evaluable patients (7%) showed partial response (PR) and 34 (83%) had stable disease (SD) for a disease control rate (DCR) of 90% (95% confidence interval [CI] 76.9-97.3%). Duration of PR was 125-401 days; median SD duration was 297 days (min-max, 50-1519 days). Median progression-free survival was 19.5 months (95% CI 10.4-28.5 months). Carcinoid symptoms of flushing, diarrhea, or both improved in 50%, 41%, and 39% of affected patients, respectively. For the first time, this study describes that a second-generation mTOR pathway inhibitor can result in highly durable tumor regression and control of NET carcinoid symptoms. The manageable safety profile, high DCR, and durable response, coupled with reduction in carcinoid symptoms refractory to SSA, make CC-223 a promising agent for further development.

BackgroundAdavosertib (AZD1775) is a first-in-class, selective, small-molecule inhibitor of Wee1.ObjectiveThe safety, tolerability, pharmacokinetics, and efficacy of adavosertib monotherapy were evaluated in patients with various solid-tumor types and molecular profiles.Patients and MethodsEligible patients had the following: confirmed diagnosis of ovarian cancer (OC), triple-negative breast cancer (TNBC), or small-cell lung cancer (SCLC); previous treatment for metastatic/recurrent disease; and measurable disease. Patients were grouped into six matched cohorts based on tumor type and presence/absence of biomarkers and received oral adavosertib 175 mg twice a day on days 1–3 and 8–10 of a 21-day treatment cycle.ResultsEighty patients received treatment in the expansion phase; median total treatment duration was 2.4 months. The most common treatment-related adverse events (AEs) were diarrhea (56.3%), nausea (42.5%), fatigue (36.3%), vomiting (18.8%), and decreased appetite (12.5%). Treatment-related grade ≥ 3 AEs and serious AEs were reported in 32.5% and 10.0% of patients, respectively. AEs led to dose interruptions in 22.5%, reductions in 11.3%, and discontinuations in 16.3% of patients. One patient died following serious AEs of deep vein thrombosis (treatment related) and respiratory failure (not treatment related). Objective response rate, disease control rate, and progression-free survival were as follows: 6.3%, 68.8%, 4.5 months (OC BRCA wild type); 3.3%, 76.7%, 3.9 months (OC BRCA mutation); 0%, 69.2%, 3.1 months (TNBC biomarker [CCNE1/MYC/MYCL1/MYCN] non-amplified [NA]); 0%, 50%, 2 months (TNBC biomarker amplified); 8.3%, 33.3%, 1.3 months (SCLC biomarker NA); and 0%, 33.3%, 1.2 months (SCLC biomarker amplified).ConclusionAdavosertib monotherapy was tolerated and demonstrated some antitumor activity in patients with advanced solid tumors.Trial RegistrationClinicalTrials.gov identifier NCT02482311; registered June 2015.

Summary Introduction Aldoxorubicin, a prodrug of doxorubicin, binds covalently to serum albumin in the bloodstream and accumulates in tumors. Aldoxorubicin can be administered at doses several-fold higher than doxorubicin can, without associated acute cardiotoxicity. Purpose This study fully evaluated the pharmacokinetic profile of aldoxorubicin (serum and urine). Methods Eighteen patients with advanced solid tumors received aldoxorubicin 230 or 350 mg/m 2 (equivalent in drug load to doxorubicin at doses of 170 or 260 mg/m 2 , respectively) once every 21 days. Blood samples were taken in cycle 1 before aldoxorubicin infusion, and at 5, 15, 30, and 60 min, and at 2, 4, 8, 12, 16, 24, 48, and 72 h after infusion. Urine samples were taken in cycle 1 at 24, 48, and 72 h after infusion. Limited blood sampling was done in cycle 3, before aldoxorubicin infusion, and at 60 min and at 2, 4, and 8 h after infusion. Results The long mean half-life (20.1–21.1 h), narrow mean volume of distribution (3.96–4.08 L/m 2 ), and slow mean clearance rate (0.136–0.152 L/h/m 2 ) suggest that aldoxorubicin is stable in circulation and does not accumulate readily in body compartments outside of the bloodstream. Very little doxorubicin and its major metabolite doxorubicinol, which has been implicated in doxorubicin-associated cardiotoxicity, are excreted in urine. This might explain the lack of cardiotoxicity observed thus far with aldoxorubicin. Conclusions Our findings support dosing and administration schemas used in an ongoing phase 3 clinical study of aldoxorubicin in soft tissue sarcoma, and phase 2 clinical studies in small cell lung cancer, glioblastoma, and Kaposi’s sarcoma.

Background IMO-2055 is a Toll-like receptor 9 (TLR9) agonist that potentially enhances the efficacy of antitumor agents through immune stimulation. The objective of this phase Ib dose-escalation trial (3 + 3 design) was to determine the recommended phase II dose (RP2D) of IMO-2055 when combined with erlotinib and bevacizumab in patients with advanced non-small cell lung cancer (NSCLC). Methods Patients with stage 3/4 NSCLC and progressive disease (PD) following chemotherapy received IMO-2055 0.08, 0.16, 0.32, or 0.48 mg/kg once weekly plus erlotinib 150 mg daily and bevacizumab 15 mg/kg every 3 weeks. Patients could receive treatment until PD or unacceptable toxicity. Results Thirty-six patients were enrolled; 35 received at least one treatment dose. Two dose-limiting toxicities were observed across the dose range (Grade 3 dehydration and fatigue) with neither suggestive of a consistent toxicity pattern. IMO-2055 0.32 mg/kg was adopted as RP2D based on clinical and pharmacodynamic data. The most common treatment-emergent adverse events (TEAEs) were diarrhea (74 %), nausea (51 %), fatigue (51 %), rash (51 %), and injection-site reactions (49 %). Four patients experienced serious TEAEs considered to be study drug related. Five patients died, all due to PD. High-grade neutropenia and electrolyte disturbances previously reported with TLR9 agonists combined with platinum-based therapy were not observed in this study. Five of 33 patients evaluable for response (15 %) achieved partial response; another 20 (61 %) had stable disease, including 13 with stable disease ≥4 months. Conclusions IMO-2055 demonstrated good tolerability and possible antitumor activity in combination with erlotinib and bevacizumab in heavily pretreated patients with advanced NSCLC.

This phase I study aimed at determining the maximum tolerated dose (MTD) and characterizing the safety, tolerability, pharmacokinetics (PKs), and efficacy of pasireotide in patients with advanced neuroendocrine tumors (NETs). Patients were enrolled in two phases: dose-escalation phase (to determine the MTD) at a starting dose of 80 mg pasireotide long-acting release (LAR) i.m. followed by a dose-expansion phase (to evaluate safety and prelimi-nary efficacy). Associations between PK/pharmacodynamic parameters and clinical outcomes were evaluated using linear regression analysis. A total of 29 patients were treated with 80 mg (n=13) and 120 mg (n=16) doses. Most common primary tumor sites included small intestine (44.8%), pancreas (24.1%), and lung (17.2%). No protocol-defined dose-limiting toxicities were observed in the study; however, in post hoc analysis, a higher incidence of bradycardia (heart rate [HR] <40 beats per minute [bpm]) was observed with 120 mg (31.3%) vs 80 mg (0%). Two partial responses (PRs) were observed, both in the 120 mg dose cohort. Pasireotide concentrations correlated with tumor shrinkage, although the association was not statistically significant ( =0.08). Among the biomarkers analyzed, insulin-like growth factor 1 (IGF-1) showed a decreasing trend with increasing pasireotide concentration, while chromogranin A (CgA) and neuron-specific enolase (NSE) levels did not show any dose-response relationship. The most common adverse events in any dose group were hyperglycemia, fatigue, and nausea. MTD was defined at 120 mg for pasireotide LAR in patients with advanced NETs. Although objective radiographic responses were rarely observed with somatostatin analogs, two PRs were observed among 16 patients in the 120 mg cohort. Bradycardia (HR <40 bpm) appears to be a dose-limiting effect; however, the mechanism and clinical significance are uncertain. This study was registered with clinicaltrials.gov (NCT01364415).

Background We evaluated the antitumor activity and safety of avelumab, a human anti–PD-L1 IgG1 antibody, as first-line switch-maintenance (1 L-mn) or second-line (2 L) treatment in patients with advanced gastric/gastroesophageal cancer (GC/GEJC) previously treated with chemotherapy. Methods In a phase 1b expansion cohort, patients without (1 L-mn) or with (2 L) disease progression following first-line chemotherapy for advanced GC/GEJC received avelumab 10 mg/kg intravenously every 2 weeks. Endpoints included best overall response, progression-free survival (PFS), overall survival (OS), and safety. Results Overall, 150 patients were enrolled (1 L-mn, n  = 90; 2 L, n  = 60) and median follow-up in the 1 L-mn and 2 L subgroups was 36.0 and 33.7 months, respectively. The confirmed objective response rate was 6.7% in both subgroups (95% CI, 2.5–13.9% and 1.8–16.2%, respectively), including complete responses in 2.2% of the 1 L-mn subgroup ( n  = 2). In the 1 L-mn and 2 L subgroups, median duration of response was 21.4 months (95% CI, 4.0–not estimable) and 3.5 months (95% CI, 2.8–8.3) and disease control rates were 56.7 and 28.3%, respectively. Median PFS in the 1 L-mn and 2 L subgroups was 2.8 months (95% CI, 2.3–4.1) and 1.4 months (95% CI, 1.3–1.5), with 6-month PFS rates of 23.0% (95% CI, 14.7–32.4%) and 7.9% (95% CI, 2.6–17.2%), and median OS was 11.1 months (95% CI, 8.9–13.7) and 6.6 months (95% CI, 5.4–9.4), respectively. In the 1 L-mn subgroup, median OS measured from start of 1 L chemotherapy was 18.7 months (95% CI, 15.4–20.6). Across both subgroups, 20.7% had an infusion-related reaction of any grade. Other common treatment-related adverse events (TRAEs) of any grade included fatigue (10.0%) and nausea (6.7%). Treatment-related serious adverse events occurred in 4.0% of patients. Overall, 8.7% had a grade ≥3 TRAE, including 1 treatment-related death. Conclusion Avelumab showed clinical activity and an acceptable safety profile in patients with GC/GEJC. Trial registration ClinicalTrials.gov NCT01772004 ; registered 21 January 2013.