Manish R. Sharma

Randomized Phase II Trials: A Long-term Investment With Promising Returns

Given the multitude of novel anticancer drugs and the limited resources available to study them, phase II trials should identify drugs with the highest probability of succeeding in subsequent phase III trials. Currently, single-arm phase II trial results are interpreted relative to historical control subjects, introducing selection bias and confounding that may limit the validity of the conclusions. The rate of success (defined as a statistically significant difference between arms) in phase III oncology trials is only 40%, suggesting that current phase II trials are insufficiently informative. However, simulation studies suggest that randomized phase II trials would have lower error rates and greater predictive power for phase III results. Randomized phase II trials may also be more informative than single-arm phase II trials because of the hypotheses being tested, the variety of possible endpoints, and the opportunities for biomarker discovery. There are a wide variety of randomized phase II designs that can be used, including the randomized discontinuation design, the delayed-start design, adaptive (Bayesian) designs, selection designs, and phase II/III designs. The barriers to widespread adoption of randomized phase II trials include time to completion, sample size considerations, and ethical concerns, but none are insurmountable. We conclude that randomized phase II trials are a worthy investment considering finite patient and financial resources and should be the rule rather than the exception for evaluating novel therapies in oncology.

Role of randomized phase III trials in an era of effective targeted therapies

In the era of cytotoxic therapies, tumor regression has rarely been observed in phase I trials and randomized controlled trials have usually been required to demonstrate modest improvements over prevailing standards of care. In the era of effective targeted therapies, drugs such as vemurafenib and crizotinib have demonstrated convincing efficacy in early clinical testing, raising the question of whether randomized phase III trials are necessary and feasible before drug approval. Since 1992, the FDA has approved a number of drugs without data from confirmatory clinical trials as part of the accelerated approval process. While this initiative has largely been successful in bringing effective drugs to the market more quickly, there is much to be learned from case studies of drugs, such as gefitinib, which subsequently failed to gain full approval. In this Review, we use a number of historical examples to make the case that it may be reasonable to consider foregoing randomized phase III trials for certain drugs before drug approval. We explore the consequences (both good and bad) of foregoing randomized phase III trials and propose criteria that might be used to select drugs for consideration of such an approach.

A phase I study of sirolimus and bevacizumab in patients with advanced malignancies.

BACKGROUND We performed a single institution, phase I study of sirolimus and bevacizumab, in order to determine the dose limiting toxicity (DLT) and recommended phase II doses. PATIENTS AND METHODS Eligible patients had previously treated advanced malignancies and were enrolled in three cohorts. Sirolimus 90 mg PO weekly (45 mg on days 1 and 2) was combined with bevacizumab 7.5mg/kg (cohort #1) or bevacizumab 15 mg/kg (cohort #2) IV q3weeks. Sirolimus 4 mg PO daily was combined with bevacizumab 15 mg/kg IV q3weeks (cohort #3). RESULTS Twenty-eight patients enrolled. The most common tumour types were colorectal (21%), head/neck (14%), and renal cell (11%). No DLTs were observed in cohorts #1 (4 patients) and #2 (12 patients), while two DLTs (grade 3 confusion and grade 3 fatigue) were observed in the first six patients in cohort #3 (12 patients). The most common grade 3 toxicities were fatigue (18%), hypertension (14%) and anorexia (11%). There were no responses, but one patient has had stable disease for 78 weeks. CONCLUSIONS The combination of sirolimus and bevacizumab at full doses is tolerable in the majority of patients. The availability and cost of sirolimus compared with other mTOR inhibitors make this an attractive agent to combine with bevacizumab.

Resampling phase III data to assess phase II trial designs and endpoints

Purpose: The best phase II design and endpoint for growth inhibitory agents is controversial. We simulated phase II trials by resampling patients from a positive (sorafenib vs. placebo; TARGET) and a negative (AE941 vs. placebo) phase III trial in metastatic renal cancer to compare the ability of various designs and endpoints to predict the known results. Experimental Design: A total of 770 and 259 patients from TARGET and the AE 941 trial, respectively, were resampled (5,000 replicates) to simulate phase II trials with α = 0.10 (one-sided). Designs/endpoints: single arm, two-stage with response rate (RR) by Response Evaluation Criteria in Solid Tumors (RECIST; 37 patients); and randomized, two arm (20–35 patients per arm) with RR by RECIST, mean log ratio of tumor sizes (log ratio), progression-free survival (PFS) rate at 90 days (PFS-90), and overall PFS. Results: Single-arm trials were positive with RR by RECIST in 55% and 1% of replications for sorafenib and AE 941, respectively. Randomized trials versus placebo with 20 patients per arm were positive with RR by RECIST in 55% and 7%, log ratio in 88% and 25%, PFS-90 in 64% and 15%, and overall PFS in 69% and 9% of replications for sorafenib and AE 941, respectively. Conclusions: Compared with the single-arm design and the randomized design comparing PFS, the randomized phase II design with the log ratio endpoint has greater power to predict the positive phase III result of sorafenib in renal cancer, but a higher false positive rate for the negative phase III result of AE 941. Clin Cancer Res; 18(8); 2309–15. ©2012 AACR.

Genomic Heterogeneity as a Barrier to Precision Medicine in Gastroesophageal Adenocarcinoma

Gastroesophageal adenocarcinoma (GEA) is a lethal disease where targeted therapies, even when guided by genomic biomarkers, have had limited efficacy. A potential reason for the failure of such therapies is that genomic profiling results could commonly differ between the primary and metastatic tumors. To evaluate genomic heterogeneity, we sequenced paired primary GEA and synchronous metastatic lesions across multiple cohorts, finding extensive differences in genomic alterations, including discrepancies in potentially clinically relevant alterations. Multiregion sequencing showed significant discrepancy within the primary tumor (PT) and between the PT and disseminated disease, with oncogene amplification profiles commonly discordant. In addition, a pilot analysis of cell-free DNA (cfDNA) sequencing demonstrated the feasibility of detecting genomic amplifications not detected in PT sampling. Lastly, we profiled paired primary tumors, metastatic tumors, and cfDNA from patients enrolled in the personalized antibodies for GEA (PANGEA) trial of targeted therapies in GEA and found that genomic biomarkers were recurrently discrepant between the PT and untreated metastases. Divergent primary and metastatic tissue profiling led to treatment reassignment in 32% (9/28) of patients. In discordant primary and metastatic lesions, we found 87.5% concordance for targetable alterations in metastatic tissue and cfDNA, suggesting the potential for cfDNA profiling to enhance selection of therapy.Significance: We demonstrate frequent baseline heterogeneity in targetable genomic alterations in GEA, indicating that current tissue sampling practices for biomarker testing do not effectively guide precision medicine in this disease and that routine profiling of metastatic lesions and/or cfDNA should be systematically evaluated. Cancer Discov; 8(1); 37-48. ©2017 AACR.See related commentary by Sundar and Tan, p. 14See related article by Janjigian et al., p. 49This article is highlighted in the In This Issue feature, p. 1.

Evaluation of food effect on pharmacokinetics of vismodegib in advanced solid tumor patients

Purpose: Vismodegib, an orally bioavailable small-molecule Smoothened inhibitor, is approved for treatment of advanced basal cell carcinoma (BCC). We conducted a pharmacokinetic study of vismodegib in patients with advanced solid tumors to explore the effects of food on drug exposure. Experimental Design: In part I, patients were randomized to fasting overnight (FO), a high fat meal (HF), or a low fat meal (LF) before a single dose of vismodegib 150 mg. Plasma concentrations of vismodegib were determined by a validated liquid chromatography-tandem mass spectrometry assay. Primary endpoints were Cmax and area under the curve (AUC0–168). In part II, patients randomized to FO or HF in part I took vismodegib 150 mg daily after fasting; those randomized to LF took it after a meal. Primary endpoints after two weeks were Cmax and AUC0–24. Results: Sixty (22 FO, 20 HF, 18 LF) and 52 (25 fasting, 27 fed) patients were evaluable for primary endpoints in parts I and II, respectively. Mean Cmax and AUC0–168 after a single dose were higher in HF than FO patients [ratios of geometric means (90% CI) = 1.75 (1.30, 2.34) and 1.74 (1.25, 2.42), respectively]. There were no significant differences in Cmax or AUC0–24 between fasting and fed groups after daily dosing. The frequencies of drug-related toxicities were similar in both groups. Conclusions: A HF meal increases plasma exposure to a single dose of vismodegib, but there are no pharmacokinetic or safety differences between fasting and fed groups at steady-state. Vismodegib may be taken with or without food for daily dosing. Clin Cancer Res; 19(11); 3059–67. ©2013 AACR.

Resampling the N9741 Trial to Compare Tumor Dynamic Versus Conventional End Points in Randomized Phase II Trials

PURPOSE The optimal end point for randomized phase II trials of anticancer therapies remains controversial. We simulated phase II trials by resampling patients from N9741, a randomized phase III trial of chemotherapy regimens for metastatic colorectal cancer, and compared the power of various end points to detect the superior therapy (FOLFOX [infusional fluorouracil, leucovorin, and oxaliplatin] had longer overall survival than both IROX [irinotecan plus oxaliplatin] and IFL [irinotecan and bolus fluorouracil plus leucovorin]). METHODS Tumor measurements and progression-free survival (PFS) data were obtained for 1,471 patients; 1,002 had consistently measured tumors and were resampled (5,000 replicates) to simulate two-arm, randomized phase II trials with α = 0.10 (one sided) and 20 to 80 patients per arm. End points included log ratio of tumor size at 6, 12, and 18 weeks relative to baseline; time to tumor growth (TTG), estimated using a nonlinear mixed-effects model; and PFS. Arms were compared using rank sum tests for log ratio and TTG and a log-rank test for PFS. RESULTS For FOLFOX versus IFL, TTG and PFS had similar power, with both exceeding the power of log ratio at 18 weeks; for FOLFOX versus IROX, TTG and log ratio at 18 weeks had similar power, with both exceeding the power of PFS. The best end points exhibited > 80% power with 60 to 80 patients per arm. CONCLUSION TTG is a powerful end point for randomized phase II trials of cytotoxic therapies in metastatic colorectal cancer; it was either comparable or superior to PFS and log ratio at 18 weeks. Additional studies will be needed to clarify the potential of TTG as a phase II end point.

Models of Excellence: Improving Oncology Drug Development

Simulations based on disease‐progression models and phase II trial results can predict phase III results and have the potential to improve oncology drug development by informing end‐of‐phase II decisions (EOP2Ds). Many barriers impede effective use of modeling and simulation (M&S) for EOP2Ds in oncology: concerns about model validity, lack of access to M&S results and patient‐level data, limited awareness of M&S among academic oncologists, and inexperience fitting M&S into the drug development timeline.

Severe irinotecan-induced toxicity in a patient with UGT1A1 28 and UGT1A1 6 polymorphisms.

Many studies have demonstrated the impact of UGT1A1 on toxicity of irinotecan. In particular, patients bearing UGT1A1 28 (TA 7/7) have a higher risk of severe neutropenia and diarrhea. Based on this, prescribers of irinotecan are advised that patients with UGT1A1 28 (TA 7/7) should start with a reduced dose of irinotecan, although a particular dose is not specified. Research in Asian countries has shown a lower incidence of UGT1A1 28 (TA 7/7), while UGT1A1 6 (A/A) is more often found and is associated with severe irinotecan-related neutropenia. We report here a case of a metastatic colorectal cancer patient who is heterozygous for the UGT1A1 28 polymorphism (TA 6/7) as well as the UGT1A1 6 polymorphism (G/A). The patient was treated with FOLFIRI for 9 cycles and underwent two irinotecan dose reductions according to pharmacokinetic data regarding exposure to the active metabolite, SN-38. Simultaneous heterozygous UGT1A1 28 and UGT1A1 6 polymorphisms may produce higher exposure to SN-38 and a higher risk of adverse effects related to irinotecan. Additional studies will be necessary to determine the optimal starting dose of irinotecan for patients with both UGT1A1 28 and UGT1A1 6 polymorphisms.

GI cancers in 2010: New standards and a predictive biomarker for adjuvant therapy.

Randomized phase III trials have established new standards of care for advanced biliary cancer, HER2-positive advanced gastric or gastro-esophageal junction cancer, and preliminarily, for metastatic pancreatic cancer. There is now a validated predictive biomarker to guide use of adjuvant chemotherapy in patients with stage II colon cancer.