A. Benjamin Suttle

Phase I Trial of Pazopanib in Patients with Advanced Cancer

Purpose: The safety, pharmacokinetics, and clinical activity of pazopanib (GW786034), an oral angiogenesis inhibitor targeting vascular endothelial growth factor receptor, platelet-derived growth factor receptor, and c-Kit, were evaluated in patients with advanced-stage refractory solid tumors. Experimental Design: Patients were enrolled into sequential dose-escalating cohorts (50 mg three times weekly to 2,000 mg once daily and 300-400 mg twice daily). Escalation or deescalation was based on toxicities observed in the preceding dose cohort. Pharmacokinetic and biomarker samples were obtained. Clinical response was assessed every 9 weeks. Results: Sixty-three patients were treated (dose escalation, n = 43; dose expansion, n = 20). Hypertension, diarrhea, hair depigmentation, and nausea were the most frequent drug-related adverse events, the majority of which were of grade 1/2. Hypertension was the most frequent grade 3 adverse event. Four patients experienced dose-limiting toxicities at 50 mg, 800 mg, and 2,000 mg once daily. A plateau in steady-state exposure was observed at doses of ≥800 mg once daily. The mean elimination half-life at this dose was 31.1 hours. A mean target trough concentration (C24) ≥15 μg/mL (34 μmol/L) was achieved at 800 mg once daily. Three patients had partial responses (two confirmed, one unconfirmed), and stable disease of ≥6 months was observed in 14 patients; clinical benefit was generally observed in patients who received doses of ≥800 mg once daily or 300 mg twice daily. Conclusion: Pazopanib was generally well tolerated and showed antitumor activity across various tumor types. A monotherapy dose of 800 mg once daily was selected for phase II studies.

A Phase I/II Trial of Pazopanib in Combination with Lapatinib in Adult Patients with Relapsed Malignant Glioma

Purpose: Increased mitogenic signaling and angiogenesis, frequently facilitated by somatic activation of EGF receptor (EGFR; ErbB1) and/or loss of PTEN, and VEGF overexpression, respectively, drive malignant glioma growth. We hypothesized that patients with recurrent glioblastoma would exhibit differential antitumor benefit based on tumor PTEN/EGFRvIII status when treated with the antiangiogenic agent pazopanib and the ErbB inhibitor lapatinib. Experimental Design: A phase II study evaluated the antitumor activity of pazopanib 400 mg/d plus lapatinib 1,000 mg/d in patients with grade 4 malignant glioma and known PTEN/EGFRvIII status not receiving enzyme-inducing anticonvulsants (EIAC). The phase II study used a two-stage Green–Dahlberg design for futility. An independent, parallel phase I component determined the maximum-tolerated regimen (MTR) of pazopanib and lapatinib in patients with grade 3/4 glioma receiving EIACs. Results: The six-month progression-free survival (PFS) rates in phase II (n = 41) were 0% and 15% in the PTEN/EGFRvIII-positive and PTEN/EGFRvIII-negative cohorts, respectively, leading to early termination. Two patients (5%) had a partial response and 14 patients (34%) had stable disease lasting 8 or more weeks. In phase I (n = 34), the MTR was not reached. On the basis of pharmacokinetic and safety review, a regimen of pazopanib 600 mg plus lapatinib 1,000 mg, each twice daily, was considered safe. Concomitant EIACs reduced exposure to pazopanib and lapatinib. Conclusions: The antitumor activity of this combination at the phase II dose tested was limited. Pharmacokinetic data indicated that exposure to lapatinib was subtherapeutic in the phase II evaluation. Evaluation of intratumoral drug delivery and activity may be essential for hypothesis-testing trials with targeted agents in malignant glioma. Clin Cancer Res; 19(4); 900–8. ©2012 AACR.

Vascular endothelial growth factor inhibition is not an effective therapeutic strategy for relapsed or refractory multiple myeloma: a phase 2 study of pazopanib (GW786034)

To the editor: Vascular endothelial growth factor (VEGF) stimulates plasma cell proliferation and migration in vitro, and preclinical studies have demonstrated that these effects can be blocked by inhibition of VEGF receptors (VEGFRs) in multiple myeloma (MM) cell lines.[1][1] Pazopanib (GW786034

Phase I Study of Pazopanib in Combination with Weekly Paclitaxel in Patients with Advanced Solid Tumors

PURPOSE To evaluate the maximum tolerated regimen (MTR), dose-limiting toxicities, and pharmacokinetics of pazopanib, an oral small-molecule tyrosine kinase inhibitor of vascular endothelial growth factor receptor, platelet-derived growth factor receptor, and c-Kit, in combination with paclitaxel. PATIENTS AND METHODS Pazopanib was given daily with weekly paclitaxel on days 1, 8, and 15 every 28 days. Dose levels of pazopanib (mg/day)/paclitaxel (mg/m(2)) were 400/15, 800/15, 800/50, and 800/80. An expanded cohort was enrolled at the MTR. Plasma samples were collected to evaluate the effect of pazopanib, an inhibitor of cytochrome P450 (CYP)3A4, on the pharmacokinetics of paclitaxel, a CYP3A4 and CYP2C8 substrate. RESULTS Of 26 enrolled patients, 17 were treated at the MTR of 800 mg pazopanib and 80 mg/m(2) paclitaxel. Dose-limiting toxicities included a grade 3 abscess and grade 2 hyperbilirubinemia. Other toxicities included elevated liver transaminases and diarrhea. Six patients (23%) had partial responses and 15 patients (58%) had stable disease. Administration of 800 mg pazopanib resulted in a 14% lower paclitaxel clearance and a 31% higher paclitaxel maximal concentration than with administration of paclitaxel alone at 15, 50, and 80 mg/m(2). At the MTR, coadministration of 800 mg pazopanib and 80 mg/m(2) paclitaxel resulted in a 26% higher geometric mean paclitaxel area under the curve. CONCLUSION Pazopanib, at a dose of 800 mg daily, can be safely combined with a therapeutic dose of paclitaxel at 80 mg/m(2) when administered on days 1, 8, and 15, every 28 days. The observed greater plasma concentrations of paclitaxel given concurrently with pazopanib suggest that pazopanib is a weak inhibitor of CYP3A4 and CYP2C8.

Phase I Study of Pazopanib in Combination with Paclitaxel and Carboplatin Given Every 21 Days in Patients with Advanced Solid Tumors

Several phase III trials have shown that the addition of an antiangiogenic agent to conventional chemotherapy can improve clinical benefit in patients with advanced solid tumors. This study examined the feasibility of combining pazopanib (Votrient), an oral antiangiogenic agent, with paclitaxel and carboplatin. This 3 + 3 dose-escalation phase I study evaluated the maximum-tolerated regimen (MTR) of daily pazopanib in combination with paclitaxel 175 mg/m2 and carboplatin [dosed at area under the curve (AUC) 5 or 6] given every 21 days in patients with advanced solid tumors. Plasma samples were collected to evaluate the effect of pazopanib on the pharmacokinetics of paclitaxel and carboplatin. Thirty-four patients were enrolled. The MTR was paclitaxel 175 mg/m2 and carboplatin AUC5 with pazopanib 200 mg. The most common dose-limiting toxicities were neutropenia and thrombocytopenia. Two patients with esophageal cancer had a complete response and four patients, one each with breast, small-cell lung, pancreatic, and gastroesophageal junction cancer, had partial responses. Pazopanib at 200 mg increased paclitaxel maximal concentration (Cmax) by 43% and carboplatin (AUC5 or AUC6) Cmax by 54%. Paclitaxel and carboplatin given every 21 days at standard doses was not feasible in combination with the monotherapy pazopanib dose of 800 mg daily because of dose-limiting myelosuppression. Coadministration of pazopanib increased exposure to paclitaxel and carboplatin and likely contributed to this effect. Given the antitumor activity of this regimen, further studies are underway to determine a clinically tolerable schedule of pazopanib with paclitaxel and carboplatin. Mol Cancer Ther; 11(8); 1820–8. ©2012 AACR.

Phase I Study of Pazopanib in Patients with Advanced Solid Tumors and Hepatic Dysfunction: A National Cancer Institute Organ Dysfunction Working Group Study

Purpose: Pazopanib is a potent, multitargeted receptor tyrosine kinase inhibitor; however, there is limited information regarding the effects of liver function on pazopanib metabolism and pharmacokinetics. The objective of this study was to establish the maximum-tolerated dose (MTD) and pharmacokinetic profile of pazopanib in patients with varying degrees of hepatic dysfunction. Experimental Design: Patients with any solid tumors or lymphoma were stratified into four groups based on the degree of hepatic dysfunction according to the National Cancer Institute Organ Dysfunction Working Group (NCI-ODWG) criteria. Pazopanib was given orally once a day on a 21-day cycle. A modified 3+3 design was used. Results: Ninety-eight patients were enrolled. Patients in the mild group tolerated 800 mg per day. The moderate and severe groups tolerated 200 mg per day. Pharmacokinetic data in the mild group were similar to the data in the normal group. Comparison of the median Cmax and area under the curve [AUC(0–24)] in the moderate or severe groups at 200 mg per day to the values in the normal and mild groups at 800 mg per day indicated less than dose–proportional systemic exposures in patients with moderate and severe hepatic impairment. This suggests that the lower maximum-tolerated dose in the moderate and severe group is not due to a decrease in drug clearance or alteration in the proportion of metabolites. Conclusions: In patients with mild liver dysfunction, pazopanib is well tolerated at the Food and Drug Administration (FDA)–approved dose of 800 mg per day. Patients with moderate and severe liver dysfunction tolerated 200 mg per day. Clin Cancer Res; 19(13); 3631–9. ©2013 AACR.

The DOT1L inhibitor pinometostat reduces H3K79 methylation and has modest clinical activity in adult acute leukemia

Pinometostat (EPZ-5676) is a first-in-class small-molecule inhibitor of the histone methyltransferase disrupter of telomeric silencing 1-like (DOT1L). In this phase 1 study, pinometostat was evaluated for safety and efficacy in adult patients with advanced acute leukemias, particularly those involving mixed lineage leukemia (MLL) gene rearrangements (MLL-r) resulting from 11q23 translocations. Fifty-one patients were enrolled into 6 dose-escalation cohorts (n = 26) and 2 expansion cohorts (n = 25) at pinometostat doses of 54 and 90 mg/m2 per day by continuous intravenous infusion in 28-day cycles. Because a maximum tolerated dose was not established in the dose-escalation phase, the expansion doses were selected based on safety and clinical response data combined with pharmacodynamic evidence of reduction in H3K79 methylation during dose escalation. Across all dose levels, plasma pinometostat concentrations increased in an approximately dose-proportional fashion, reaching an apparent steady-state by 4-8 hours after infusion, and rapidly decreased following treatment cessation. The most common adverse events, of any cause, were fatigue (39%), nausea (39%), constipation (35%), and febrile neutropenia (35%). Overall, 2 patients, both with t(11;19), experienced complete remission at 54 mg/m2 per day by continuous intravenous infusion, demonstrating proof of concept for delivering clinically meaningful responses through targeting DOT1L using the single agent pinometostat in MLL-r leukemia patients. Administration of pinometostat was generally safe, with the maximum tolerated dose not being reached, although efficacy as a single agent was modest. This study demonstrates the therapeutic potential for targeting DOT1L in MLL-r leukemia and lays the groundwork for future combination approaches in this patient population. This clinical trial is registered at www.clinicaltrials.gov as NCT01684150.

Bayesian Methods for Pharmacokinetic/Pharmacodynamic Modeling of Pazopanib‐Induced Increases in Blood Pressure and Transaminases

Relationships between plasma pazopanib concentrations and the probability of elevations in blood pressure, a marker of vascular endothelial growth factor receptor inhibition, and alanine aminotransferase (ALT) were investigated with logistic regression models. Data from a Phase I dose‐escalation study in cancer patients (n = 57) were examined to determine the relationship between steady‐state trough plasma pazopanib concentrations (Cτ) and a clinically significant blood pressure increase, using a Bayesian logistic regression model. Data from 5 monotherapy studies in cancer patients (n = 344) were pooled to investigate the relationship between Cτ and maximum ALT ≥ 3× the upper limit of normal (ULN), using a Bayesian logistic regression model incorporating an asymptote. Both models were fit using WinBUGS. The median (95% credible interval, CrI) Cτ at which the probability of a clinically significant increase in blood pressure was 50% (EC50) was 12.3 μg/mL (6.12, 18.4). The median (95% CrI) EC50 for the maximum probability of ALT ≥ 3 × ULN was 15.4 μg/mL (3.8, 41.2) and the median (95% CrI) maximum probability of ALT ≥ 3 × ULN was 21% (14.5, 43.1). Results suggest that dose adjustments could be useful in managing the potential for hepatotoxicity.