PT - JOURNAL ARTICLE AU - Jeffrey R Simard AU - Klaus Michelsen AU - Yan Wang AU - Chunhua Yang AU - Beth Youngblood AU - Barbara Grubinska AU - Kristin Taborn AU - Daniel J Gillie AU - Kevin Cook AU - Kyu Chung AU - Alexander M. Long AU - Brian E Hall AU - Paul L Shaffer AU - Robert S. Foti AU - Jacinthe Gingras TI - <strong>Modulation of ligand-gated glycine receptors via functional monoclonal antibodies</strong> AID - 10.1124/jpet.121.001026 DP - 2022 Jan 01 TA - Journal of Pharmacology and Experimental Therapeutics PG - JPET-AR-2021-001026 4099 - http://jpet.aspetjournals.org/content/early/2022/08/04/jpet.121.001026.short 4100 - http://jpet.aspetjournals.org/content/early/2022/08/04/jpet.121.001026.full AB - Ion channels are targets of considerable therapeutic interest to address a wide variety of neurological indications, including pain perception. Current pharmacological strategies have focused mostly on small molecule approaches which can be limited by selectivity requirements within members of a channel family or superfamily. Therapeutic antibodies have been proposed, designed and characterized to alleviate this selectivity limitation, however there are no FDA-approved therapeutic antibody-based drugs targeting ion channels on the market to date. Here, in an effort to identify novel classes of engineered ion channel modulators for potential neurological therapeutic applications, we report the generation and characterization of six (EC50 &lt; 25nM) Cys-loop receptor family monoclonal antibodies with modulatory function against rat and human glycine receptor alpha 1 (GlyRa1) and/or GlyRa3. These antibodies have activating (i.e.; positive modulator) or inhibiting (i.e.; negative modulator) profiles. Moreover, GlyRa3 selectivity was successfully achieved for two of the three positive modulators identified. When dosed intravenously, the antibodies achieved sufficient brain exposure to cover their calculated in vitro EC50 values. When compared head-to-head at identical exposures, the GlyRa3-selective antibody showed a more desirable safety profile over the non-selective antibody, thus demonstrating, for the first time, an advantage for GlyRa3-selectivity. Our data show that ligand-gated ion channels of the glycine receptor family within the CNS can be functionally modulated by engineered biologics in a dose-dependent manner and that, despite high protein homology between the alpha subunits, selectivity can be achieved within this receptor family resulting in future therapeutic candidates with more desirable drug safety profiles. Significance Statement We present immunization and multi-platform screening approaches to generate a diverse library of functional antibodies (agonist, potentiator or inhibitory) raised against human glycine receptors (GlyRs). We also demonstrate the feasibility of acquiring alpha subunit selectivity, a desirable therapeutic profile. When tested in vivo, these tool molecules demonstrated an increased safety profile in favor of GlyRa3-selectivity. To our knowledge, these are the first reported functional GlyR antibodies that may open new avenues to treating CNS diseases with subunit selective biologics.