Equitable inclusion of diverse populations in oncology clinical trials: deterrents and drivers

The burden of cancer exerts a disproportionate impact across different regions and population subsets. Disease-specific attributes, coupled with genetic and socioeconomic factors, significantly influence cancer treatment outcomes. Precision oncology promises the development of safe and effective options for specific ethnic phenotypes and clinicodemographic profiles. Currently, clinical trials are concentrated in resource-rich geographies with younger, healthier, white, educated, and empowered populations. Vulnerable and marginalized people are often deprived of opportunities to participate in clinical trials. Despite consistent endeavors by regulators, industry, and other stakeholders, factors including diversity in trial regulations and patient and provider-related cultural, logistic, and operational barriers limit the inclusiveness of clinical trials. Understanding and addressing these constraints by collaborative actions involving regulatory initiatives, industry, patient advocacy groups, community engagement in a culturally sensitive manner, and designing and promoting decentralized clinical trials are vital to establishing a clinical research ecosystem that promotes equity in the representation of population subgroups.

Safety and early efficacy results from a phase I study of volociximab (V) in combination with carboplatin (C) and paclitaxel (P) in patients (pts) with advanced non small cell lung cancer (NSCLC)

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Background: Volociximab is a chimeric monoclonal antibody that blocks fibronectin binding to α5β1 and induces apoptosis in proliferating endothelial cells. Its anti-angiogenic actions are independent of the VEGF pathway. This is the first clinical study of voloxicimab in patients with advanced NSCLC. Methods: This phase 1b multi-center open-label, dose-escalation study was designed to determine the maximum tolerated dose of V in combination with full doses of C (AUC=6mg/ml.min) P (200mg/m2) with cycles repeated every 3 wks for a maximum of 6 cycles followed by a maintenance treatment with V alone. Eligible pts had histologically confirmed untreated stage IIIb or IV NSCLC. In cohorts 1 and 2, pts received V at 10 mg/kg and 20mg/kg IV, respectively, on days 1 and 8, of the first 21 day cycle then every 21 days. In cohort 3, pts received V 30 mg/kg IV every 21 days from day 1. We present here the interim safety analysis and RECIST response data of the combination therapy. Results: A total of 22 patients (9, 6 and 7 in cohorts 1, 2 and 3 respectively) who received at least one dose of treatment constitute the safety population. Reported salient adverse events (any grade) were constipation (68%), asthenia (64%), nausea (59%), arthralgia (55%) and paresthesia (46%). Grade 3 bowel obstruction in one patient was considered a DLT in cohort 2. No DLT's were observed in cohort 3. Seven pts reported at least one serious adverse event (all Grade 3) including deep vein thrombosis (1), peripheral arterial occlusion (1), proteinuria (1), pneumonitis (1), small intestinal obstruction (1), pleural effusion (1), hypoxia (1), dehydration (1) and orthostatic hypotension (1). Partial response was seen in 6 pts and stable disease in 12 out of 18 pts who were evaluable for response by RECIST. Conclusions: The highest dose of V tested (30 mg/kg q3w) in combination with CP appears well tolerated and the regimen has promising clinical activity in advanced NSCLC.

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A Phase I study of infusional vinblastine in combination with the P-glycoprotein antagonist PSC 833 (valspodar)

BACKGROUND

PSC 833 is a second-generation P-glycoprotein (Pgp) antagonist developed to reverse multidrug resistance (MDR). The authors conducted a Phase I study of orally administered PSC 833 in combination with vinblastine administered as a 5-day continuous infusion.

METHODS

Seventy-nine patients with advanced malignant disease were enrolled in the trial and treated with escalating doses of PSC 833. Pharmacokinetic interactions between PSC 833 and vinblastine were anticipated. Accordingly, when dose limiting toxicities were observed, the dose of vinblastine was reduced as PSC 833 was escalated. Three schedules and two formulations of PSC 833 were used in the study.

RESULTS

The maximum tolerated doses of PSC 833 were 12.5 mg/kg orally every 12 hours for 8 days for the liquid formulation in combination with 0.9 mg/m(2) per day vinblastine as a continuous intravenous infusion (CIV) for 5 days; and 4 mg/kg orally every 6 hours for 8 days for the microemulsion formulation in combination with 0.6 mg/m(2) per day vinblastine CIV for 5 days. The principal toxicities for PSC 833 were ataxia and paresthesias and for the combination, constipation, fever. and neutropenia. Increased oral bioavailability and increased peak and trough concentrations were observed with the microemulsion formulation. Significant interpatient variability in pharmacokinetic parameters was observed. Ten patients studied at the MTD for PSC 833 (4 mg/kg orally every 6 hours for 8 days) had inhibition of rhodamine efflux from CD56 positive peripheral lymphocytes as a surrogate for Pgp antagonism. Among 43 evaluable patients with clear cell carcinoma of the kidney, 3 patients had complete responses, and 1 patient had a partial response.

CONCLUSIONS

PSC 833 in combination with vinblastine can be administered safely to patients provided the vinblastine dose is adjusted for pharmacokinetic interactions. The high interpatient variability is a significant confounding factor. Surrogate studies with CD56 positive cells suggest that Pgp inhibition in the clinical setting is achievable. Improved methods for predicting pharmacokinetic interactions should improve future studies.

Phase I study of infusional paclitaxel in combination with the P-glycoprotein antagonist PSC 833

PURPOSE

PSC 833 (valspodar) is a second-generation P-glycoprotein (Pgp) antagonist developed to reverse multidrug resistance. We conducted a phase I study of a 7-day oral administration of PSC 833 in combination with paclitaxel, administered as a 96-hour continuous infusion.

PATIENTS AND METHODS

Fifty patients with advanced cancer were enrolled onto the trial. PSC 833 was administered orally for 7 days, beginning 72 hours before the start of the paclitaxel infusion. Paclitaxel dose reductions were planned because of the pharmacokinetic interactions known to occur with PSC 833.

RESULTS

In combination with PSC 833, maximum-tolerated doses were defined as paclitaxel 13.1 mg/m(2)/d continuous intravenous infusion (CIVI) for 4 days without filgrastim, and paclitaxel 17.5 mg/m(2)/d CIVI for 4 days with filgrastim support. Dose-limiting toxicity for the combination was neutropenia. Statistical analysis of cohorts revealed similar mean steady-state concentrations (C(pss)) and areas under the concentration-versus-time curve (AUCs) when patients received paclitaxel doses of 13.1 or 17.5 mg/m(2)/d for 4 days with PSC 833, as when they received a paclitaxel dose of 35 mg/m(2)/d for 4 days without PSC 833. However, the effect of PSC 833 on paclitaxel pharmacokinetics varied greatly among individual patients, although a surrogate assay using CD56+ cells suggested inhibition of Pgp was complete or nearly complete at low concentrations of PSC 833. Responses occurred in three of four patients with non-small-cell lung cancer, and clinical benefit occurred in five of 10 patients with ovarian carcinoma.

CONCLUSION

PSC 833 in combination with paclitaxel can be administered safely to patients provided the paclitaxel dose is reduced to compensate for the pharmacokinetic interaction. Surrogate studies with CD56+ cells indicate that the maximum-tolerated dose for PSC 833 gives serum levels much higher than those required to block Pgp. The variability in paclitaxel pharmacokinetics, despite complete inhibition of Pgp in the surrogate assay, suggests that other mechanisms, most likely related to P450, contribute to the pharmacokinetic interaction. Future development of combinations such as this should include strategies to predict pharmacokinetics of the chemotherapeutic agent. This in turn will facilitate dosing to achieve comparable CPss and AUCs.

SmcL, a novel membrane-damaging virulence factor in Listeria

We describe here the fourth listerial membrane-damaging virulence factor, a sphingomyelinase C (SMase) that is produced specifically by the ruminant pathogen Listeria ivanovii. Its coding gene, smcL, is a monocistron expressed independently of PrfA. The smcL product, SmcL, is highly similar to the staphylococcal beta-toxin and is responsible for the differential hemolytic properties of L. ivanovii (bizonal hemolysis and CAMP-like reaction with R. equi). The role of SmcL in virulence was assessed by gene disruption and complementation. Our data show that SmcL mediates disruption of the membrane of primary phagosomes, thereby promoting bacterial intracellular proliferation. They also suggest that SmcL may play a role in host tropism. smcL is located in LIPI-2, a novel 18-kb pathogenicity island which also contains a cluster of internalin genes. LIPI-2 is unstable, L. ivanovii-specific and required for full virulence in mice and lambs.