Jeffrey G. Supko

Preclinical pharmacologic evaluation of geldanamycin as an antitumor agent

The plasma pharmacokinetics of the antitumor antibiotic geldanamycin (GM; NSC 122750), a naturally occurring benzoquinoid ansamycin, was characterized in mice and a beagle dog. Concentrations of GM well above 0.1 μg/ml, which was typically effective against neoplastic cell lines responsive to the drug in vitro, were achieved in the plasma of the mice and the dog treated by i.v. injection. However, the systemic duration of the drug was relatively short. Plasma levels decayed below 0.1 μg/ml within 3–4 h after administration of the apparent maximum tolerated doses, which were approximately 20 mg/kg for the mice and 4 mg/kg for the dog. The drug exhibited linear pharmacokinetic behavior within the dose ranges studied. However, there were significant interspecies differences in its disposition. Whereas the mean biological half-life of GM was slightly longer in the mice (77.7 min) than in the dog (57.9 min), its mean residence time in the dog (46.6 min) was more than twofold greater than that observed in the mice (20.7 min). Nevertheless, the drug was cleared from plasma much faster by the dog (49.4 ml/min per kg) than by the mice (30.5 ml/min per kg). These apparent anomalies were principally associated with differences in the relative significance of the terminal phase upon overall drug disposition. The liver appeared to be the principal target organ of acute drug toxicity in the dog. Doses of 2.0 and 4.2 mg/kg both produced elevations in serum levels of the transaminases and other indicators of liver function characteristic of acute hepatic necrosis. Additional effects included symptoms of minor gastrointestinal toxicity and alterations in serum chemistry parameters consistent with less severe nephrotoxicity. Drug-related toxicity appeared to be reversible. In consideration of the potential for acute hepatotoxic reactions to GM, as well as to the other benzoquinoid ansamycins based upon structural analogy, additional pharmacological and therapeutic information is required to ascertain whether these compounds are viable candidates for clinical development.

Identification of genotype-correlated sensitivity to selective kinase inhibitors by using high-throughput tumor cell line profiling

Kinase inhibitors constitute an important new class of cancer drugs, whose selective efficacy is largely determined by underlying tumor cell genetics. We established a high-throughput platform to profile 500 cell lines derived from diverse epithelial cancers for sensitivity to 14 kinase inhibitors. Most inhibitors were ineffective against unselected cell lines but exhibited dramatic cell killing of small nonoverlapping subsets. Cells with exquisite sensitivity to EGFR, HER2, MET, or BRAF kinase inhibitors were marked by activating mutations or amplification of the drug target. Although most cell lines recapitulated known tumor-associated genotypes, the screen revealed low-frequency drug-sensitizing genotypes in tumor types not previously associated with drug susceptibility. Furthermore, comparing drugs thought to target the same kinase revealed striking differences, predictive of clinical efficacy. Genetically defined cancer subsets, irrespective of tissue type, predict response to kinase inhibitors, and provide an important preclinical model to guide early clinical applications of novel targeted inhibitors.

Phase II and Pharmacokinetic Study of Ecteinascidin 743 in Patients With Progressive Sarcomas of Soft Tissues Refractory to Chemotherapy

PURPOSE To assess the efficacy of the marine-derived alkaloid ecteinascidin 743 (ET-743) in patients with soft tissue sarcomas that progressed despite prior conventional chemotherapy and to characterize the pharmacokinetic profiles of ET-743 in this patient population. PATIENTS AND METHODS Thirty-six previously treated soft tissue sarcoma patients from three institutions received ET-743 as a 24-hour continuous intravenous (IV) infusion at a dose of 1,500 microg/m(2) every 3 weeks. Pharmacokinetic studies were also performed. Patients were restaged every two cycles for response by objective criteria. RESULTS Objective responses were observed in three patients, with one complete response and two partial responses, for an overall response rate of 8% (95% CI, 2% to 23%). Responses were durable for up to 20 months. Two minor responses (43% and 47% tumor reduction) were observed, for an overall clinical benefit rate of 14%. The predominant toxicities were neutropenia and self-limited transaminitis of grade 3 to 4 severity in 34% and 26% of patients, respectively. The estimated 1-year time to progression and overall survival rates were 9% (95% CI, 3% to 27%) and 53% (95% CI, 39% to 73%), respectively. The maximum observed plasma concentration and total plasma clearance of ET-743 (mean +/- standard deviation), 1.04 +/- 0.48 ng/mL and 35.6 +/- 16.2 L/h/m(2), respectively, were consistent with previously reported values from phase I studies of the drug given as a 24-hour IV infusion. CONCLUSION ET-743 is a promising new option for the management of several histologic subtypes of sarcoma. Durable objective responses were obtained in a subset of sarcoma patients with disease progression despite prior chemotherapy. Additionally, the relatively high survival rate noted in this series of previously treated patients further justifies development of this agent.

Phase I Clinical Trial of Recombinant Human Endostatin Administered as a Short Intravenous Infusion Repeated Daily

PURPOSE To perform a phase I trial of recombinant human endostatin (rhEndostatin; EntreMed, Rockville, MD) given as a daily 20-minute intravenous (IV) injection in adult patients with refractory solid tumors. PATIENTS AND METHODS The daily dose was increased from 15 to 240 mg/m(2) by a factor of 100% in cohorts of three patients. In the absence of dose-limiting toxicity, uninterrupted treatment was continued until the tumor burden increased by more than 50% from baseline. Correlative studies included dynamic contrast-enhanced magnetic resonance imaging of tumor blood flow, urinary vascular endothelial growth factor and basic fibroblast growth factor levels, rhEndostatin serum pharmacokinetics, and monitoring of circulating antibodies to rhEndostatin. RESULTS There were no notable treatment related toxicities among 15 patients receiving a total of 50 monthly cycles of rhEndostatin. One patient with a pancreatic neuroendocrine tumor had a minor response and two patients showed disease stabilization. Linearity in the pharmacokinetics of rhEndostatin was indicated by dose-proportionate increases in the area under the curve for the first dose and the peak serum concentration at steady state. Daily systemic exposure to rhEndostatin in patients receiving 240 mg/m(2)/d was approximately 50% lower than that provided by the therapeutically optimal dose in preclinical studies. CONCLUSION rhEndostatin administered as a 20-minute daily IV injection at doses up to 240 mg/m(2) showed no significant toxicities. Evidence of clinical benefit was observed in three patients. Due to high variability between the peak and trough serum concentrations associated with the repeated short IV infusion schedule, daily serum drug levels only briefly exceeded concentrations necessary for in vitro antiangiogenic effects.

Inhibitors of HIV nucleocapsid protein zinc fingers as candidates for the treatment of AIDS.

Strategies for the treatment of human immunodeficiency virus-type 1 (HIV-1) infection must contend with the obstacle of drug resistance. HIV-1 nucleocapsid protein zinc fingers are prime antiviral targets because they are mutationally intolerant and are required both for acute infection and virion assembly. Nontoxic disulfide-substituted benzamides were identified that attack the zinc fingers, inactivate cell-free virions, inhibit acute and chronic infections, and exhibit broad antiretroviral activity. The compounds were highly synergistic with other antiviral agents, and resistant mutants have not been detected. Zinc finger-reactive compounds may offer an anti-HIV strategy that restricts drug-resistance development.

A phase I/II trial of hydroxychloroquine in conjunction with radiation therapy and concurrent and adjuvant temozolomide in patients with newly diagnosed glioblastoma multiforme

Preclinical studies indicate autophagy inhibition with hydroxychloroquine (HCQ) can augment the efficacy of DNA-damaging therapy. The primary objective of this trial was to determine the maximum tolerated dose (MTD) and efficacy of HCQ in combination with radiation therapy (RT) and temozolomide (TMZ) for newly diagnosed glioblastoma (GB). A 3 + 3 phase I trial design followed by a noncomparative phase II study was conducted in GB patients after initial resection. Patients received HCQ (200 to 800 mg oral daily) with RT and concurrent and adjuvant TMZ. Quantitative electron microscopy and immunoblotting were used to assess changes in autophagic vacuoles (AVs) in peripheral blood mononuclear cells (PBMC). Population pharmacokinetic (PK) modeling enabled PK-pharmacodynamic correlations. Sixteen phase I subjects were evaluable for dose-limiting toxicities. At 800 mg HCQ/d, 3/3 subjects experienced Grade 3 and 4 neutropenia and thrombocytopenia, 1 with sepsis. HCQ 600 mg/d was found to be the MTD in this combination. The phase II cohort (n = 76) had a median survival of 15.6 mos with survival rates at 12, 18, and 24 mo of 70%, 36%, and 25%. PK analysis indicated dose-proportional exposure for HCQ. Significant therapy-associated increases in AV and LC3-II were observed in PBMC and correlated with higher HCQ exposure. These data establish that autophagy inhibition is achievable with HCQ, but dose-limiting toxicity prevented escalation to higher doses of HCQ. At HCQ 600 mg/d, autophagy inhibition was not consistently achieved in patients treated with this regimen, and no significant improvement in overall survival was observed. Therefore, a definitive test of the role of autophagy inhibition in the adjuvant setting for glioma patients awaits the development of lower-toxicity compounds that can achieve more consistent inhibition of autophagy than HCQ.

Ecteinascidin-743 (ET-743) for Chemotherapy-Naive Patients With Advanced Soft Tissue Sarcomas: Multicenter Phase II and Pharmacokinetic Study

PURPOSE To evaluate the response rate, toxicity profile, and pharmacokinetics of ecteinascidin-743 (ET-743) as first-line therapy in patients with unresectable advanced soft tissue sarcoma (STS). PATIENTS AND METHODS Thirty-six patients with STS were enrolled onto the study between September 1999 and August 2000. Patients were treated with 1.5 mg/m2 of ET-743 given as a 24-hour continuous intravenous (IV) infusion every 21 days. Pharmacokinetic sampling was performed in 23 patients. RESULTS One complete and five partial responses were achieved in 35 assessable patients for an overall response rate of 17.1% (95% CI, 6.6% to 33.6%). In addition, one patient had a minor response, leading to an overall clinical benefit of 20%. Neutropenia and transaminitis were the main grade 3 to 4 toxicities, which occurred in 33% and 36% of the patients. The estimated 1-year progression-free and overall survival rates were 21% (95% CI, 11% to 41%) and 72% (95% CI, 59% to 88%), respectively. Total body clearance (L/h) was not significantly correlated with body-surface area (r = -0.28; P = .21). Mild hepatic impairment or the extent of prior cytotoxic therapy does not seem to contribute significantly to the high interpatient variability (49%) in the clearance of this drug. Severity of treatment-related toxicity was not correlated with pharmacokinetic variables. CONCLUSION ET-743 demonstrates clinical activity as first-line therapy against STS with acceptable toxicity. Additional studies to establish empirical dosing guidelines may be necessary to improve the safety of the drug in patients with varying degrees of hepatic dysfunction and definitively establish the role of ET-743 for patients with these malignancies.

Hydrocarbon double-stapling remedies the proteolytic instability of a lengthy peptide therapeutic

The pharmacologic utility of lengthy peptides can be hindered by loss of bioactive structure and rapid proteolysis, which limits bioavailability. For example, enfuvirtide (Fuzeon, T20, DP178), a 36-amino acid peptide that inhibits human immunodeficiency virus type 1 (HIV-1) infection by effectively targeting the viral fusion apparatus, has been relegated to a salvage treatment option mostly due to poor in vivo stability and lack of oral bioavailability. To overcome the proteolytic shortcomings of long peptides as therapeutics, we examined the biophysical, biological, and pharmacologic impact of inserting all-hydrocarbon staples into an HIV-1 fusion inhibitor. We find that peptide double-stapling confers striking protease resistance that translates into markedly improved pharmacokinetic properties, including oral absorption. We determined that the hydrocarbon staples create a proteolytic shield by combining reinforcement of overall α-helical structure, which slows the kinetics of proteolysis, with complete blockade of peptide cleavage at constrained sites in the immediate vicinity of the staple. Importantly, double-stapling also optimizes the antiviral activity of HIV-1 fusion peptides and the antiproteolytic feature extends to other therapeutic peptide templates, such as the diabetes drug exenatide (Byetta). Thus, hydrocarbon double-stapling may unlock the therapeutic potential of natural bioactive polypeptides by transforming them into structurally fortified agents with enhanced bioavailability.

Dependence on the MUC1-C oncoprotein in non-small cell lung cancer cells.

Non–small cell lung cancer (NSCLC) cells are often associated with constitutive activation of the phosphoinositide 3-kinase (PI3K) → Akt → mTOR pathway. The mucin 1 (MUC1) heterodimeric glycoprotein is aberrantly overexpressed in NSCLC cells and induces gene signatures that are associated with poor survival of NSCLC patients. The present results show that the MUC1 C-terminal subunit (MUC1-C) cytoplasmic domain associates with PI3K p85 in NSCLC cells. We show that inhibition of MUC1-C with cell-penetrating peptides blocks this interaction with PI3K p85 and suppresses constitutive phosphorylation of Akt and its downstream effector, mTOR. In concert with these results, treatment of NSCLC cells with the MUC1-C peptide inhibitor GO-203 was associated with downregulation of PI3K → Akt signaling and inhibition of growth. GO-203 treatment was also associated with increases in reactive oxygen species (ROS) and induction of necrosis by a ROS-dependent mechanism. Moreover, GO-203 treatment of H1975 (EGFR L858R/T790M) and A549 (K-Ras G12S) xenografts growing in nude mice resulted in tumor regressions. These findings indicate that NSCLC cells are dependent on MUC1-C both for activation of the PI3K → Akt pathway and for survival. Mol Cancer Ther; 10(5); 806–16. ©2011 AACR.

Phase I and Pharmacokinetic Study of Bortezomib in Combination with Idarubicin and Cytarabine in Patients with Acute Myelogenous Leukemia

Purpose: Proteasome inhibition results in cytotoxicity to the leukemia stem cell in vitro. We conducted this phase I study to determine if the proteasome inhibitor bortezomib could be safely added to induction chemotherapy in patients with acute myelogenous leukemia (AML). Experimental Design: Bortezomib was given on days 1, 4, 8, and 11 at doses of 0.7, 1.0, 1.3, or 1.5 mg/m2 with idarubicin 12 mg/m2 on days 1 to 3 and cytarabine 100 mg/m2/day on days 1 to 7. Results: A total of 31 patients were enrolled. The median age was 62 years, and 16 patients were male. Nine patients had relapsed AML (ages, 18-59 years, n = 4 and ≥60 years, n = 5). There were 22 patients of ≥60 years with previously untreated AML (eight with prior myelodysplasia/myeloproliferative disorder or cytotoxic therapy). All doses of bortezomib, up to and including 1.5 mg/m2, were tolerable. Nonhematologic grade 3 or greater toxicities included 12 hypoxia (38%; 11 were grade 3), 4 hyperbilirubinemia (13%), and 6 elevated aspartate aminotransferase (19%). Overall, 19 patients (61%) achieved complete remission (CR) and three had CR with incomplete platelet recovery. Pharmacokinetic studies revealed that the total body clearance of bortezomib decreased significantly (P < 0.01, N = 26) between the first (mean ± SD, 41.9 ± 17.1 L/h/m2) and third (18.4 ± 7.0 L/h/m2) doses. Increased bone marrow expression of CD74 was associated with CR. Conclusions: The combination of bortezomib, idarubicin, and cytarabine showed a good safety profile. The recommended dose of bortezomib for phase II studies with idarubicin and cytarabine is 1.5 mg/m2.