A CD80-Biased CTLA4-Ig Fusion Protein with Superior In Vivo Efficacy by Simultaneous Engineering of Affinity, Selectivity, Stability, and FcRn Binding.

Affinity- and stability-engineered variants of CTLA4-Ig fusion molecules with enhanced pharmacokinetic profiles could yield improved therapies with the potential of higher efficacy and greater convenience to patients. In this study, to our knowledge, we have, for the first time, used in vitro evolution to simultaneously optimize CTLA4 affinity and stability. We selected for improved binding to both ligands, CD80 and CD86, and screened as dimeric Fc fusions directly in functional assays to identify variants with stronger suppression of in vitro T cell activation. The majority of CTLA4 molecules showing the largest potency gains in primary in vitro and ex vivo human cell assays, using PBMCs from type 1 diabetes patients, had significant improvements in CD80, but only modest gains in CD86 binding. We furthermore observed different potency rankings between our lead molecule MEDI5265, abatacept, and belatacept, depending on which type of APC was used, with MEDI5265 consistently being the most potent. We then created fusions of both stability- and potency-optimized CTLA4 moieties with human Fc variants conferring extended plasma t1/2 In a cynomolgus model of T cell-dependent Ab response, the CTLA4-Ig variant MEDI5265 could be formulated at >100 mg/ml for s.c. administration and showed superior efficacy and significantly prolonged serum t1/2 The combination of higher stability and potency with prolonged pharmacokinetics could be compatible with very infrequent, s.c. dosing while maintaining a similar level of immune suppression to more frequently and i.v. administered licensed therapies.

Assessing safety of extractables from materials and leachables in pharmaceuticals and biologics - Current challenges and approaches.

Leachables from pharmaceutical container closure systems can present potential safety risks to patients. Extractables studies may be performed as a risk mitigation activity to identify potential leachables for dosage forms with a high degree of concern associated with the route of administration. To address safety concerns, approaches to toxicological safety evaluation of extractables and leachables have been developed and applied by pharmaceutical and biologics manufacturers. Details of these approaches may differ depending on the nature of the final drug product. These may include application, the formulation, route of administration and length of use. Current regulatory guidelines and industry standards provide general guidance on compound specific safety assessments but do not provide a comprehensive approach to safety evaluations of leachables and/or extractables. This paper provides a perspective on approaches to safety evaluations by reviewing and applying general concepts and integrating key steps in the toxicological evaluation of individual extractables or leachables. These include application of structure activity relationship studies, development of permitted daily exposure (PDE) values, and use of safety threshold concepts. Case studies are provided. The concepts presented seek to encourage discussion in the scientific community, and are not intended to represent a final opinion or "guidelines."

Pharmacokinetic and pharmacodynamic comparability study of moxetumomab pasudotox, an immunotoxin targeting CD22, in cynomolgus monkeys.

Moxetumomab pasudotox is an immunotoxin currently being investigated in patients for the treatment of CD22-expressing B-cell malignancies. A single-cycle pharmacokinetic (PK)-pharmacodynamic (PD) study was conducted in cynomolgus monkeys for PK comparability assessment and population PK-PD modeling after major manufacturing process and site changes. Primates were randomized by body weight and baseline CD22 lymphocyte counts to receive intravenous administrations of 1 mg/kg moxetumomab pasudotox (n = 12/group) on Days 1, 3, and 5. PK and B-lymphocyte count data were modeled using a population approach. The 90% confidence intervals of the geometric mean ratios of PK exposure were within the 80%-125% range. The B lymphocytes were depleted to a similar extent, and the immunogenicity incidences were similar across the two groups. The B-cell depletion was described by a novel lifespan model in which moxetumomab pasudotox induced random destruction of B cells in each aging compartment. The endogenous de novo influx from bone marrow was subject to a negative feedback mechanism. The estimated B cell apparent lifespan was 51 days. Covariate analysis confirmed that the manufacturing change had no impact on PK or PD of moxetumomab pasudotox. Results from this study supported continued clinical investigation of moxetumomab pasudotox using the new material.

Challenges of general safety evaluations of biologics compared to small molecule pharmaceuticals in animal models.

IMPORTANCE OF THE FIELD: The prediction of human toxicity by employing animal models for nonclinical safety evaluation of pharmaceuticals poses numerous challenges. Each type, biologics, vaccines and small molecules, has unique features, which may impact the ability to effectively assess safety. AREAS COVERED IN THIS REVIEW: The importance of taking a case-by-case approach is highlighted in this review of the challenges encountered in general safety evaluations for biologics and vaccines compared to small molecules. WHAT THE READER WILL GAIN: The reader will gain insights in specific issues related to building a successful predictive nonclinical safety program for biologics. TAKE HOME MESSAGE: While there is fair concordance for small molecules, animal models used for the safety evaluation of biologics may have limitations with regard to human relevance. For small molecules, this is commonly because of differences in metabolism profiles or off-target effects. For biologics, which are highly targeted molecules, it may be because of differences in physiological processes or biologic pathways that limit pharmacologic relevance. For vaccines or immunomodulatory biologics, it may be related to the complexities of modeling the human immune system in a nonhuman species. While international guidances are available to govern the nonclinical safety assessment process for human pharmaceuticals (such as ICH M3), in many instances a case-by-case approach is employed for novel agents.