1stOncology™: Cancer Intelligence Service – Page 16454 – 1stOncology is recognized as a Top 10 Global Pharma Analytic Provider

Recent advances in the development of new auristatins: structural modifications and application in antibody drug conjugates.

Dolastatin 10 is a powerful antineoplastic agent and microtubule inhibitor that was discovered by Pettit et al. and published in 1987. Since then, many research groups have engaged in SAR studies of synthetic analogues, termed &quot;auristatins&quot;. It was eventually discovered that auristatins are of great value as payloads in antibody drug conjugates (ADCs), which led to the FDA-approved ADC brentuximab vedotin (Seattle Genetics). Currently, over 30 ADCs in clinical trials employ auristatins as payloads, and there is a great interest in the research community, both on academic and industrial sides, to further study these analogues. This review will provide an overview of the recent advancements in auristatin development spanning a time frame of about the past ten years. The main focus will be to describe structural changes made to the auristatin peptide and their resulting biological activities in tumor cell proliferation assays. Selected ADC examples will also be described.

Schedule your 30 min Free 1stOncology Demo!
Discover why more than 1,500 members use 1stOncology™ to excel in:

Early/Late Stage Pipeline Development - Target Scouting - Clinical Biomarkers - Indication Selection & Expansion - BD&L Contacts - Conference Reports - Combinatorial Drug Settings - Companion Diagnostics - Drug Repositioning - First-in-class Analysis - Competitive Analysis - Deals & Licensing

Schedule Your 30 min Free Demo!

Phenotype of TPBG Gene Replacement in the Mouse and Impact on the Pharmacokinetics of an Antibody-Drug Conjugate.

The use of predictive preclinical models in drug discovery is critical for compound selection, optimization, preclinical to clinical translation, and strategic decision-making. Trophoblast glycoprotein (TPBG), also known as 5T4, is the therapeutic target of several anticancer agents currently in clinical development, largely due to its high expression in tumors and low expression in normal adult tissues. In this study, mice were engineered to express human TPBG under endogenous regulatory sequences by replacement of the murine Tpbg coding sequence. The gene replacement was considered functional since the hTPBG knockin (hTPBG-KI) mice did not exhibit clinical observations or histopathological phenotypes that are associated with Tpbg gene deletion, except in rare instances. The expression of hTPBG in certain epithelial cell types and in different microregions of the brain and spinal cord was consistent with previously reported phenotypes and expression patterns. In pharmacokinetic studies, the exposure of a clinical-stage anti-TPBG antibody-drug conjugate (ADC), A1mcMMAF, was lower in hTPBG-KI versus wild-type animals, which was evidence of target-related increased clearance in hTPBG-KI mice. Thus, the hTPBG-KI mice constitute an improved system for pharmacology studies with current and future TPBG-targeted therapies and can generate more precise pharmacokinetic and pharmacodynamic data. In general the strategy of employing gene replacement to improve pharmacokinetic assessments should be broadly applicable to the discovery and development of ADCs and other biotherapeutics.

Surface-expressed insulin receptors as well as IGF-I receptors both contribute to the mitogenic effects of human insulin and its analogues.

There is a medical need for new insulin analogues. Yet, molecular alterations to the insulin molecule can theoretically result in analogues with carcinogenic effects. Preclinical carcinogenicity risk assessment for insulin analogues rests to a large extent on mitogenicity assays in cell lines. We therefore optimized mitogenicity assay conditions for a panel of five cell lines. All cell lines expressed insulin receptors (IR), IGF-I receptors (IGF-IR) and hybrid receptors, and in all cell lines, insulin as well as the comparator compounds X10 and IGF-I caused phosphorylation of the IR as well as IGF-IR. Insulin exhibited mitogenicity EC(50) values in the single-digit nanomolar to picomolar range. We observed correlations across cell types between (i) mitogenic potency of insulin and IGF-IR/IR ratio, (ii) Akt phosphorylation and mitogenic potency and (iii) Akt phosphorylation and IR phosphorylation. Using siRNA-mediated knockdown of IR and IGF-IR, we observed that in HCT 116 cells the IR appeared dominant in driving the mitogenic response to insulin, whereas in MCF7 cells the IGF-IR appeared dominant in driving the mitogenic response to insulin. Together, our results show that the IR as well as IGF-IR may contribute to the mitogenic potency of insulin. While insulin was a more potent mitogen than IGF-I in cells expressing more IR than IGF-IR, the hyper-mitogenic insulin analogue X10 was a more potent mitogen than insulin across all cell types, supporting that the hyper-mitogenic effect of X10 involves the IR as well as the IGF-IR. These results are relevant for preclinical safety assessment of developmental insulin analogues.
Copyright © 2014 John Wiley &amp; Sons, Ltd.

Sclerostin inhibition promotes TNF-dependent inflammatory joint destruction.

Sclerostin, an inhibitor of the Wnt/β-catenin pathway, has anti-anabolic effects on bone formation by negatively regulating osteoblast differentiation. Mutations in the human sclerostin gene (SOST) lead to sclerosteosis with progressive skeletal overgrowth, whereas sclerostin-deficient (Sost(-/-)) mice exhibit increased bone mass and strength. Therefore, antibody-mediated inhibition of sclerostin is currently being clinically evaluated for the treatment of postmenopausal osteoporosis in humans. We report that in chronic TNFα (tumor necrosis factor α)-dependent arthritis, fibroblast-like synoviocytes constitute a major source of sclerostin and that either the lack of sclerostin or its antibody-mediated inhibition leads to an acceleration of rheumatoid arthritis (RA)-like disease in human TNFα transgenic (hTNFtg) mice with enhanced pannus formation and joint destruction. Inhibition of sclerostin also failed to improve clinical signs and joint destruction in the partially TNFα-dependent glucose-6-phosphate isomerase-induced arthritis mouse model, but ameliorated disease severity in K/BxN serum transfer-induced arthritis mouse model, which is independent of TNF receptor signaling, thus suggesting a specific role for sclerostin in TNFα signaling. Sclerostin effectively blocked TNFα- but not interleukin-1-induced activation of p38, a key step in arthritis development, pointing to a previously unrealized protective role of sclerostin in TNF-mediated chronic inflammation. The possibility of anti-sclerostin antibody treatment worsening clinical RA outcome under chronic TNFα-dependent inflammatory conditions in mice means that caution should be taken both when considering such treatment for inflammatory bone loss in RA and when using anti-sclerostin antibodies in patients with TNFα-dependent comorbidities.
Copyright © 2016, American Association for the Advancement of Science.

OncoMed Presents GITRL-Fc Research at the AACR Annual Meeting 2016

On April 19, 2016 OncoMed Pharmaceuticals Inc. (NASDAQ:OMED), reported new data related to its GITRL-Fc immuno-oncology therapeutic candidate at the American Association of Cancer Research (AACR) (Free AACR Whitepaper) Meeting (Press release, OncoMed, APR 19, 2016, View Source [SID:1234511073]). OncoMed plans to file an Investigational New Drug (IND) application with the U.S. Food and Drug Administration (FDA) for its GITRL-Fc candidate in late 2016/early 2017.

In two poster presentations, OncoMed researchers highlighted the differentiating characteristics and preclinical efficacy of this therapeutic candidate. OncoMed’s GITRL-Fc is engineered using a novel single-gene linkerless GITR ligand trimer that binds to glucocorticoid-induced tumor necrosis factor receptor. GITRL-Fc appears to act by increasing effector T-cell activation and proliferation and reducing regulatory T-cell mediated immune suppression, resulting in a potent Th1 immune response. Single-agent GITRL-Fc demonstrated profound anti-tumor activity in multiple syngeneic mouse tumor models and achieved statistically significantly greater anti-tumor activity compared with GITR agonist antibody. Notably, GITRL-Fc did not induce the broad release of cytokines in the plasma and spleen observed with the GITR agonist antibody, suggesting the potential for an improved safety profile relative to agonist antibodies.

"We believe our approach to GITR activation, using the human ligand trimer that binds to the GITR receptor, will result in more effective activation and a more specific and potent immune response compared to other approaches. In a series of preclinical studies presented at the AACR (Free AACR Whitepaper) Annual Meeting, OncoMed’s GITRL-Fc demonstrated superior anti-tumor activity to an agonist antibody and induced complete tumor regressions as a single agent. Further, the broad cytokine release observed with GITR agonist antibodies was not observed using the GITR ligand approach," said Austin Gurney, PhD, co-Chief Scientific Officer and Senior Vice President, Molecular and Cellular Biology.

The activity of GITRL-Fc was also studied in comparison and in combination with anti-PDL1 and anti-PD1. GITRL-Fc combined with either anti-PDL1 or anti-PD1 resulted in a number of complete tumor regressions and single-agent GITRL-Fc demonstrated greater anti-tumor activity than single-agent anti-PDL1 or anti-PD1. The anti-tumor activity of GITRL-Fc in combination with either anti-PDL1 or anti-PD1 reduced tumor growth beyond that of any of the agents alone. Mice "cured" with GITRL-Fc or GITRL-Fc/anti-PDL1 or GITRL-Fc/and-PD1 combination treatments were protected from re-challenge with parental tumor cells, indicating the development of sustained anti-tumor immunologic memory.

These data were presented in Abstract #2214 "GITR ligand fusion protein (GITRL-Fc) induces T cell mediated anti-tumor immune response and can combine with anti-PDL1 to enhance anti-tumor immunity and long-term immune memory" and Abstract 3215 "GITRL-Fc can significantly reduce tumor growth by stimulating innate and adaptive immunity".