Purpose: The use of cellular and tissue-based biomaterials to treat OA and other musculoskeletal conditions has gained prominence in recent years. One such approach utilizes donated placental tissues, which contain a variety of growth factors, cytokines and anti-inflammatory mediators, as well as bioregulatory ECM macromolecules. In addition, placental tissues are immunologically privileged, and thus pose a very low risk of immunogenicity. PTP-001 is a human placental tissue-derived preparation which is in development as a biologic therapy, and which displays a multimodal mechanism of action (MOA) with the potential to promote a beneficial combination of anti-catabolic and pro-anabolic effects in the treatment of OA.
Methods: PTP-001 Preparation. PTP-001 is derived from aseptically processed placental tissues (amnion, chorion and umbilical cord) obtained from scheduled C-section births. Following cleaning, and procedures for micronization, the combined lyophilized tissues are terminally sterilized. Donor screening, tissue recovery, processing and lot release are performed in compliance with cGTP requirements and AATB Standards. Protein Biofactor Analysis. PTP-001 extracts were generated by incubation in PBS containing 2% w/v collagenase type I, and screened using custom protein multiplex arrays (Quantibody®; RayBiotech) for the presence of pro-anabolic, and anti-catabolic/anti-inflammatory biofactors. Next, a panel of therapeutically relevant, representative biofactors were chosen to perform quantitative ELISAs: bFGF as a pro-anabolic factor, TIMP-1, -2 and -3 as key anti-catabolic factors, and IL-1 receptor antagonist (IL-1Ra) as an anti-inflammatory mediator. IL-1α, and the ECM molecule fibronectin (Fn) were also assayed. Human Chondrocyte Bioassay. Chondrocytes from human OA cartilage were cultured as monolayers in the absence or presence of a catabolic stimulus (42kDa Fn fragments), and in the absence or presence of PTP-001 eluates. Culture media were analyzed by Western blotting and ELISA to determine MMP-13 protein levels; chondrocyte viability was confirmed using LIVE/DEAD reagents (Molecular Probes). Rat OA Model. PTP-001 was tested in a surgical destabilization (DMM) OA model in rats (Bolder BioPATH; n=12 animals per group). At 2 weeks post-surgery, animals received an intra-articular injection of saline, PTP-001 suspended in saline or steroid (triamcinolone) in saline. Some animals received a second injection of PTP-001 at 4 weeks post-surgery. Pain measurements (incapacitance and von Frey testing) were performed over 6 weeks post-dosing, after which the knee joints were processed for histopathologic scoring.
Results: Protein multiplex screening of PTP-001 extracts reproducibly detected over 55 biofactors relevant to growth/anabolic, signaling/adhesion, and anti-inflammatory/anti-catabolic pathways. Quantitative ELISA analysis of PTP-001 extracts from 7 individual donors demonstrated high levels of pro-anabolic (bFGF), anti-catabolic (TIMP-1,-2,-3), and anti-inflammatory (IL-1Ra) biofactors (Fig. 1). Low levels of IL-1α, and high levels of Fn were also detected. In the human chondrocyte bioassay, there was a strong induction of MMP-13 protein levels by addition of a catabolic stimulus. Addition of PTP-001 eluates resulted in a dose-dependent inhibition of MMP-13 production (Fig. 2), indicating that PTP-001 may have a protective role in OA joints by reducing levels of MMP-13 and associated ECM degradation. In the rat OA model, PTP-001 treatment resulted in significant pain reduction as assessed by hind-limb weight bearing (incapacitance; Fig. 3) and von Frey testing. In addition, PTP-001 treatment was efficacious in preventing cartilage degeneration/joint tissue damage, with significant reductions in cartilage degeneration and total joint scores, width of severe lesions, and lesion depth (Fig. 4).
Conclusions: To date, all attempts to develop disease-modifying therapies for OA have failed, principally due to lack of clinical efficacy or safety issues. Such treatments have generally focused on modulation of a single target (e.g. a specific cytokine or enzyme/protease) whereas OA is a complex, mutifactorial disease process. PTP-001 represents an effective tissue-derived treatment, with an inherent multi-modal MOA that can impact a number of pathologic pathways (including pain and tissue damage) which contribute to OA. Development of PTP-001 as a regulated biologic product, in concordance with FDA guidance, represents a safe and novel approach for the treatment of OA and other musculoskeletal conditions.
© 2020 Published by Elsevier Inc.
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