Non-mutagenic impurities - Recent industry experience of using dose durational limits in drug development.

Absence of clear guidance on the qualification threshold for non-mutagenic impurities during clinical development is a source of inconsistency in both sponsor qualification approaches and health authority requests. A survey was conducted in March 2020 with 6 member companies of the European Federation of Pharmaceutical Industries and Associations (EFPIA). Thirteen examples were gathered of where non-International Council for Harmonisation (ICH) limits have been used in regulatory submissions for various indications and stages of development, together with the regulatory outcomes. As expected, few challenges were faced in early clinical development, with health authorities generally commenting that sponsors should work towards ICH Q3A and Q3B guideline specification limits as development progresses. However, inconsistent health authority requests were noted even for early phase clinical trials in late-stage oncology patients. For an optimised use of resources, consistent approaches would have the benefit of supporting faster access of safe medicines to patients while including Replacement, Reduction and Refinement (the 3Rs) considerations with respect to animal testing.

Liposomal Irinotecan Shows a Larger Therapeutic Index than Non-liposomal Irinotecan in Patient-Derived Xenograft Models of Pancreatic Cancer.

INTRODUCTION: Liposomal irinotecan promotes controlled sustained release of irinotecan (CPT-11), therefore, we hypothesize that the therapeutic index (quantitative measurement of the relative efficacy/safety ratio of a drug) will be higher for liposomal than non-liposomal irinotecan. METHODS: We compared the therapeutic indexes of liposomal and non-liposomal irinotecan in mice bearing subcutaneous patient-derived xenograft (PDX) pancreatic tumors under dosing regimens approximating the clinical setting. Following preliminary drug sensitivity/antitumor activity analyses on three PDX tumor models, one model was selected for analyses of efficacy, biomarker, toxicology, pharmacokinetics in mice receiving liposomal irinotecan (2.5, 10, 50 mg/kg/week) or non-liposomal irinotecan (10, 25, 50 mg/kg/week). The maximum tolerated dose (MTD) for each treatment was 50 mg/kg/week. RESULTS: Using the selected IM-PAN-001 model at the MTD (both treatments, 50 mg/kg/week), antitumor activity, phospho-histone gamma-H2AX protein staining in cancer cell nuclei, histological tumor regression, and plasma levels of CPT-11 and its active metabolite SN-38 after 24 h were greater with liposomal than non-liposomal irinotecan, but tumor SN-38 levels were similar. At the lowest doses assessed, antitumor activity, histological tumor regression, and jejunum and bone marrow toxicity were similar. Based on these findings, liposomal and non-liposomal irinotecan had therapeutic indexes of 20 and 5, respectively. CONCLUSION: This non-clinical study showed a fourfold broader therapeutic index with liposomal than non-liposomal irinotecan in mice bearing IM-PAN-001 PDX pancreatic tumors, even at optimal dosing for the two drugs. These findings support the clinical benefit observed with liposomal irinotecan in patients with pancreatic cancer.

Species selection for nonclinical safety assessment of drug candidates: Examples of current industry practice.

In drug development, nonclinical safety assessment is pivotal for human risk assessment and support of clinical development. Selecting the relevant/appropriate animal species for toxicity testing increases the likelihood of detecting potential effects in humans, and although recent regulatory guidelines state the need to justify or dis-qualify animal species for toxicity testing, individual companies have developed decision-processes most appropriate for their molecules, experience and 3Rs policies. These generally revolve around similarity of metabolic profiles between toxicology species/humans and relevant pharmacological activity in at least one species for New Chemical Entities (NCEs), whilst for large molecules (biologics) the key aspect is similarity/presence of the intended human target epitope. To explore current industry practice, a questionnaire was developed to capture relevant information around process, documentation and tools/factors used for species selection. Collated results from 14 companies (Contract Research Organisations and pharmaceutical companies) are presented, along with some case-examples or over-riding principles from individual companies. As the process and justification of species selection is expected to be a topic for continued emphasis, this information could be adapted towards a harmonized approach or best practice for industry consideration.