Alain C. Mita

Survivin: Key Regulator of Mitosis and Apoptosis and Novel Target for Cancer Therapeutics

Survivin, a member of the family of inhibitor of apoptosis proteins, functions as a key regulator of mitosis and programmed cell death. Initially, survivin was described as an inhibitor of caspase-9. However, over the last years, research studies have shown that the role of survivin in cancer pathogenesis is not limited to apoptosis inhibition but also involves the regulation of the mitotic spindle checkpoint and the promotion of angiogenesis and chemoresistance. Survivin gene expression is transcriptionally repressed by wild-type p53 and can be deregulated in cancer by several mechanisms, including gene amplification, hypomethylation, increased promoter activity, and loss of p53 function. This article reviews the multiple functions of survivin in the regulation of apoptosis, the promotion of tumorigenesis, and the development of survivin inhibitors as a novel anticancer therapeutic strategy.

Phase I Trial of the Novel Mammalian Target of Rapamycin Inhibitor Deforolimus (AP23573; MK-8669) Administered Intravenously Daily for 5 Days Every 2 Weeks to Patients With Advanced Malignancies

PURPOSE This phase I trial was conducted to determine the safety, tolerability, pharmacokinetics, and pharmacodynamics of deforolimus (previously known as AP23573; MK-8669), a nonprodrug rapamycin analog, in patients with advanced solid malignancies. PATIENTS AND METHODS Patients were treated using an accelerated titration design with sequential escalating flat doses of deforolimus administered as a 30-minute intravenous infusion once daily for 5 consecutive days every 2 weeks (QDx5) in a 28-day cycle. Safety, pharmacokinetic, pharmacodynamic, and tumor response assessments were performed. RESULTS Thirty-two patients received at least one dose of deforolimus (3 to 28 mg/d). Three dose-limiting toxicity events of grade 3 mouth sores were reported. The maximum-tolerated dose (MTD) was 18.75 mg/d. Common treatment-related adverse events included reversible mouth sores and rash. Whole-blood clearance increased with dose. Pharmacodynamic analyses demonstrated mammalian target of rapamycin inhibition at all dose levels. Four patients (one each with non-small-cell lung cancer, mixed müllerian tumor [carcinosarcoma], renal cell carcinoma, and Ewing sarcoma) experienced confirmed partial responses, and three additional patients had minor tumor regressions. CONCLUSION The MTD of this phase I trial using an accelerated titration design was determined to be 18.75 mg/d. Deforolimus was well tolerated and showed encouraging antitumor activity across a broad range of malignancies when administered intravenously on the QDx5 schedule. On the basis of these overall results, a dose of 12.5 mg/d is being evaluated in phase II trials.

Phase I and Pharmacokinetic Study of XRP6258 (RPR 116258A), a Novel Taxane, Administered as a 1-Hour Infusion Every 3 Weeks in Patients with Advanced Solid Tumors

Purpose: To assess the feasibility of administering XRP6258, a new taxane with a low affinity for the multidrug resistance 1 protein, as a 1-hour i.v. infusion every 3 weeks. The study also sought to determine the maximum tolerated dose and the recommended dose, to describe the pharmacokinetic (PK) behavior of the compound, and to seek preliminary evidence of anticancer activity. Experimental Design: Twenty-five patients with advanced solid malignancies were treated with 102 courses of XRP6258 at four dose levels ranging from 10 to 25 mg/m2. Dose escalation was based on the occurrence of dose-limiting toxicity (DLT) at each dose level, provided that PK variables were favorable. The maximum tolerated dose was defined as the dose at which at least two patients developed a DLT at the first course. Results: Neutropenia was the principal DLT, with one patient experiencing febrile neutropenia and two others showing prolonged grade 4 neutropenia at the 25 mg/m2 dose level. Nonhematologic toxicities, including nausea, vomiting, diarrhea, neurotoxicity, and fatigue, were generally mild to moderate in severity. XRP6258 exhibited dose-proportional PK, a triphasic elimination profile, a long terminal half-life (77.3 hours), a high clearance (mean CL, 53.5 L/h), and a large volume of distribution (mean Vss, 2,034 L/m2). Objective antitumor activity included partial responses in two patients with metastatic prostate carcinoma, one unconfirmed partial response, and two minor responses. Conclusion: The recommended phase II dose of XRP6258 on this schedule is 20 mg/m2. The general tolerability and encouraging antitumor activity in taxane-refractory patients warrant further evaluations of XRP6258.

The molecular target of rapamycin (mTOR) as a therapeutic target against cancer.

The molecular target of rapamycin (mTOR), which is a member of the phosphoinositide 3-kinase related kinase (PIKK) family and a central modulator of cell growth, is a prime strategic target for anti-cancer therapeutic development. mTOR plays a critical role in transducing proliferative signals mediated through the phosphatidylinositol 3 kinase (PI3K)/protein kinase B (Akt) signaling pathway, principally by activating downstream protein kinases that are required for both ribosomal biosynthesis and translation of key mRNAs of proteins required for G1 to S phase traverse. By targeting mTOR, the immunsuppressant and antiproliferative agent rapamycin (RAP) inhibits signals required for cell cycle progression, cell growth, and proliferation. RAP, a complex macrolide and highly potent fungicide, immunosuppressant, and anti-cancer agent, is a highly specific inhibitor of mTOR. In essence, RAP gains function by binding to the immunophilin FK506 binding protein 12 (FKBP12) and the resultant complex inhibits the activity of mTOR. Since mTOR activates both the 40S ribosomal protein S6 kinase (p70s6k) and the eukaryotic initiation factor 4E-binding protein-1 (4E-BP1), RAP blocks activation of these downstream signaling elements, which results in cell cycle arrest in the G1 arrest. RAP also prevents cyclin-dependent kinase (cdk) activation, inhibits retinoblastoma protein (pRb) phosphorylation, and accelerates the turnover of cyclin D1 that leads to a deficienciy of active cdk4/cyclin D1 complexes, all of which potentially contribute to the prominent inhibitory effects of RAP at the G1/S phase transition. Both RAP and several RAP analogs with more favorable pharmaceutical properties have demonstrated prominent growth inhibitory effects against a broad range of human cancers in both preclinical and early clinical evaluations. This review will summarize the principal mechanisms of action of RAP and RAP derivatives and their potential utility of these agents as anti-cancer therapeutics. The preliminary results of early clinical evaluations with RAP analogs and the unique developmental challenges that lie ahead will also be discussed.

Autophagy inhibition enhances vorinostat-induced apoptosis via ubiquitinated protein accumulation

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.

A Phase I, Multicenter, Open-Label, First-in-Human, Dose-Escalation Study of the Oral Smoothened Inhibitor Sonidegib (LDE225) in Patients with Advanced Solid Tumors

Purpose: This phase I trial was undertaken to determine the maximum tolerated dose (MTD), dose-limiting toxicities (DLT), safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary antitumor activity of the novel smoothened inhibitor sonidegib (LDE225), a potent inhibitor of hedgehog signaling, in patients with advanced solid tumors. Experimental Design: Oral sonidegib was administered to 103 patients with advanced solid tumors, including medulloblastoma and basal cell carcinoma (BCC), at doses ranging from 100 to 3,000 mg daily and 250 to 750 mg twice daily, continuously, with a single-dose pharmacokinetics run-in period. Dose escalations were guided by a Bayesian logistic regression model. Safety, tolerability, efficacy, pharmacokinetics, and biomarkers in skin and tumor biopsies were assessed. Results: The MTDs of sonidegib were 800 mg daily and 250 mg twice daily. The main DLT of reversible grade 3/4 elevated serum creatine kinase (18% of patients) was observed at doses ≥ the MTD in an exposure-dependent manner. Common grade 1/2 adverse events included muscle spasm, myalgia, gastrointestinal toxicities, increased liver enzymes, fatigue, dysgeusia, and alopecia. Sonidegib exposure increased dose proportionally up to 400 mg daily, and displayed nonlinear pharmacokinetics at higher doses. Sonidegib exhibited exposure-dependent reduction in GLI1 mRNA expression. Tumor responses observed in patients with medulloblastoma and BCC were associated with evidence of hedgehog pathway activation. Conclusions: Sonidegib has an acceptable safety profile in patients with advanced solid tumors and exhibits antitumor activity in advanced BCC and relapsed medulloblastoma, both of which are strongly associated with activated hedgehog pathway, as determined by gene expression. Clin Cancer Res; 20(7); 1900–9. ©2014 AACR.

Phase I Dose-Escalation Study of JNJ-42756493, an Oral Pan-Fibroblast Growth Factor Receptor Inhibitor, in Patients With Advanced Solid Tumors

PURPOSE JNJ-42756493 is an orally administered pan-fibroblast growth factor receptor (FGFR) tyrosine kinase inhibitor. This first-in-human study evaluates the safety, pharmacokinetics, and pharmacodynamics and defines the recommended phase II dose (RP2D) of JNJ-42756493. PATIENTS AND METHODS Eligible patients with advanced solid tumors received escalating doses of JNJ-42756493 from 0.5 to 12 mg administered continuously daily or JNJ-42756493 10 or 12 mg administered intermittently (7 days on/7 days off). RESULTS Sixty-five patients were enrolled. The most common treatment-emergent adverse events included hyperphosphatemia (65%), asthenia (55%), dry mouth (45%), nail toxicity (35%), constipation (34%), decreased appetite (32%), and dysgeusia (31%). Twenty-seven patients (42%) experienced grade ≥ 3 treatment-emergent adverse events, and one dose-limiting toxicity of grade 3 ALT elevation was observed at 12 mg daily. Maximum-tolerated dose was not defined. Nine milligrams daily was considered as the initial RP2D; however, tolerability was improved with intermittent schedules, and 10 mg administered on a 7-days-on/7-days-off schedule was considered the final RP2D. Pharmacokinetics were linear, dose proportional, and predictable, with a half-life of 50 to 60 hours. Dose-dependent elevations in serum phosphate, a manifestation of pharmacodynamic effect, occurred in all patients starting at 4 mg daily. Among 23 response-evaluable patients with tumor FGFR pathway alterations, four confirmed responses and one unconfirmed partial response were observed in patients with glioblastoma and urothelial and endometrial cancer (all with FGFR2 or FGFR3 translocations); 16 patients had stable disease. CONCLUSION JNJ-42756493 administered at 10 mg on a 7-days-on/7-days-off schedule achieved exposures at which clinical responses were observed, demonstrated pharmacodynamic biomarker activity, and had a manageable safety profile.

Combined autophagy and HDAC inhibition: a phase I safety, tolerability, pharmacokinetic, and pharmacodynamic analysis of hydroxychloroquine in combination with the HDAC inhibitor vorinostat in patients with advanced solid tumors.

We previously reported that inhibition of autophagy significantly augmented the anticancer activity of the histone deacetylase (HDAC) inhibitor vorinostat (VOR) through a cathepsin D-mediated mechanism. We thus conducted a first-in-human study to investigate the safety, preliminary efficacy, pharmacokinetics (PK), and pharmacodynamics (PD) of the combination of the autophagy inhibitor hydroxychloroquine (HCQ) and VOR in patients with advanced solid tumors. Of 27 patients treated in the study, 24 were considered fully evaluable for study assessments and toxicity. Patients were treated orally with escalating doses of HCQ daily (QD) (d 2 to 21 of a 21-d cycle) in combination with 400 mg VOR QD (d one to 21). Treatment-related adverse events (AE) included grade 1 to 2 nausea, diarrhea, fatigue, weight loss, anemia, and elevated creatinine. Grade 3 fatigue and/or myelosuppression were observed in a minority of patients. Fatigue and gastrointestinal AE were dose-limiting toxicities. Six-hundred milligrams HCQ and 400 mg VOR was established as the maximum tolerated dose and recommended phase II regimen. One patient with renal cell carcinoma had a confirmed durable partial response and 2 patients with colorectal cancer had prolonged stable disease. The addition of HCQ did not significantly impact the PK profile of VOR. Treatment-related increases in the expression of CDKN1A and CTSD were more pronounced in tumor biopsies than peripheral blood mononuclear cells. Based on the safety and preliminary efficacy of this combination, additional clinical studies are currently being planned to further investigate autophagy inhibition as a new approach to increase the efficacy of HDAC inhibitors.

A Phase I Study of Eribulin Mesylate (E7389), a Mechanistically Novel Inhibitor of Microtubule Dynamics, in Patients with Advanced Solid Malignancies

Purpose: Eribulin mesylate (E7389), a non-taxane microtubule dynamics inhibitor, is a structurally simplified, synthetic analogue of halichondrin B that acts via a mechanism distinct from conventional tubulin-targeted agents. This phase I study determined the maximum tolerated dose (MTD) and pharmacokinetics of eribulin administered on a 3 of 4 week schedule in patients with advanced solid malignancies. Experimental Design: Patients received eribulin mesylate (1-hour i.v. infusion) on days 1, 8, and 15 of a 28-day cycle. Dosing began at 0.25 mg/m2 with escalation guided by dose-limiting toxicities (DLT). MTD, DLTs, safety, pharmacokinetics, and antitumor activity were characterized. Results: Thirty-two patients received eribulin mesylate (0.25, 0.5, 0.7, 1.0, or 1.4 mg/m2). Neutropenia was the principal DLT: At 1.4 mg/m2, two patients experienced grade 4 neutropenia, one of whom also developed grade 3 fatigue; three additional patients experienced grade 3 neutropenia and were not treated during cycle 1 on day 15. Therefore, the MTD was 1.0 mg/m2. Fatigue (53% overall, 13% grade 3, no grade 4), nausea (41%, all grade 1/2), and anorexia (38% overall, 3% grade 3, no grade 4) were the most common eribulin-related adverse events. Eight patients reported grade 1/2 neuropathy (no grade 3/4). Eribulin pharmacokinetics were dose-proportional over the dose range studied. One patient (cervical cancer) achieved an unconfirmed partial response lasting 79 days. Ten patients reported stable disease. Conclusions: Eribulin mesylate, given on days 1, 8, and 15 of a 28-day cycle, exhibits manageable tolerability at 1.0 mg/m2 with further dose escalation limited by neutropenia and fatigue.

Deforolimus (AP23573) a novel mTOR inhibitor in clinical development

mTOR was determined to be a promising anticancer target and several drug inhibitors of mTOR are currently in clinical development. Rapamycin (RAP) was the first mTOR inhibitor discovered. However, RAP has poor aqueous solubility and chemical stability and therefore its utilization at doses susceptible to produce an effect as an anticancer agent is limited. This represented the main rationale for developing new RAP analogs. The RAP analogs currently in clinical development as anticancer agents include temsirolimus (CCI-779), everolimus (RAD-001), and deforolimus (AP23573). These agents have demonstrated antiproliferative activity against a diverse range of malignancies in preclinical studies, and clinical evaluations have been very encouraging thus far. Deforolimus (AP23573), a non-RAP prodrug, has been tested in Phase I and II clinical trials and shows promising results in several tumor types including sarcoma. A Phase III study in patients with sarcoma is currently ongoing. The preclinical and clinical studies with deforolimus will be presented.