No abstract

Skeletal muscle is under inhibitory homeostatic regulation by multiple ligands of the transforming growth factor-β (TGFβ) superfamily. Follistatin is a secreted protein that promotes muscle growth and function by sequestering these ligands extracellularly. In the present study, we evaluated the potential of ACE-083 – a locally acting, follistatin-based fusion protein – as a novel therapeutic agent for focal or asymmetric myopathies. Characterization of ACE-083 in vitro revealed its high affinity for heparin and extracellular matrix while surface plasmon resonance and cell-based assays confirmed that ACE-083 binds and potently neutralizes myostatin, activin A, activin B and growth differentiation factor 11 (GDF11). Intramuscular administration of ACE-083 caused localized, dose-dependent hypertrophy of the injected muscle in wild-type mice and mouse models of Charcot-Marie-Tooth disease (CMT) and Duchenne muscular dystrophy, with no evidence of systemic muscle effects or endocrine perturbation. Importantly, ACE-083 also increased the force of isometric contraction in situ by the injected tibialis anterior muscle in wild-type mice and disease models and increased ankle dorsiflexion torque in CMT mice. Our results demonstrate the potential of ACE-083 as a therapeutic agent for patients with CMT, muscular dystrophy and other disorders with focal or asymmetric muscle atrophy or weakness.

Follistatin is an endogenous glycoprotein that promotes growth and repair of skeletal muscle by sequestering inhibitory ligands of the transforming growth factor-b superfamily and may therefore have therapeutic potential for neuromuscular diseases. Here, we sought to determine the suitability of a newly engineered follistatin fusion protein (FST288-Fc) to promote localized, rather than systemic, growth of skeletal muscle by capitalizing on the intrinsic heparin-binding ability of the follistatin-288 isoform. As determined by surface plasmon resonance and cell-based assays, FST288-Fc binds to activin A, activin B, myostatin (growth differentiation factor GDF8), and GDF11 with high affinity and neutralizes their activity in vitro. Intramuscular administration of FST288-Fc in mice induced robust, dose-dependent growth of the targeted muscle but not of surrounding or contralateral muscles, in contrast to the systemic effects of a locally administered fusion protein incorporating activin receptor type IIB (ActRIIB-Fc). Furthermore, systemic administration of FST288-Fc in mice did not alter muscle mass or body composition as determined by NMR, which again contrasts with the pronounced systemic activity of ActRIIB-Fc when administered by the same route. Subsequent analysis revealed that FST288-Fc in the circulation undergoes rapid proteolysis, thereby restricting its activity to individual muscles targeted by intramuscular administration. These results indicate that FST288-Fc can produce localized growth of skeletal muscle in a targeted manner with reduced potential for undesirable systemic effects. Thus, FST288-Fc and similar agents may be beneficial in the treatment of disorders with muscle atrophy that is focal, asymmetric, or otherwise heterogeneous.

TNFR2 is highly expressed on the surface of activated T effector cells, T regulatory cells and myeloid cells, and it plays essential roles in modulating the tumor microenvironment. In most cancer types, higher TNFR2 expression correlates with increased immune cell infiltration. Furthermore, the TNFR2 gene is differentially expressed in various cancer types, including breast, lung, renal, liver and skin cancers. In cancers such as head and neck cancer and cutaneous melanoma, high TNFR2 expression correlates with better overall survival. The therapeutic potential of antibodies targeting TNFR2 has been demonstrated by agonist antibodies for the T effector cells, and antibodies that antagonize or deplete the T regulatory cells and suppressive myeloid cells. We discovered novel TNFR2 antibodies that demonstrate unique mechanisms to overcome T cell exhaustion and the suppressive tumor microenvironment for more effective immunotherapy. In vitro studies have shown that our antibodies block TNFα ligand binding and potently inhibit TNFR2 signaling in the monocytic cells. Moreover, these antibodies enhance CD8 T cell function to overcome the suppressive effect from the T regulatory cells and can invigorate exhausted CD8 T cells in an FcγR-dependent manner. In a humanized mouse model, our antibodies demonstrate strong anti-tumor efficacy as single agents or in combination with a PD-L1 inhibitor. Therefore, these antibodies offer potential advantages when the tumor microenvironment is enriched in the exhausted T cells, the suppressive myeloid cells, or the regulatory T cells, as found in anti-PD-1/PD-L1 resistant and PD-1 refractory patients. In conclusion, the data obtained indicate that our TNFR2 antibodies are a novel and promising class of drug candidates for cancer immunotherapeutics. Our lead antibody is currently at the IND-enabling stage with the target of entering clinical studies in early 2022. Citation Format: Chi Shing Sum, Makenzie Danton, Qii hu, Alla Pritsker, Ray Lin, Raymond Yu, Kevin Chen, Fangqiang Tang, Thomas Pohl, Samantha Wallner, Ahmed Hassan, Huarui Lu, Haichun Huang, James Pei, Zhong Liu, Han Li, Ming Lei. Novel TNFR2 antibodies to overcome T cell exhaustion and suppressive tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1869.

No abstract