HANGZHOU, China, Sept. 9, 2025 — Biotle today announced successful preclinical pharmacokinetic/pharmacodynamic (PK/PD) results for BTL-203, a half-life–extended inhibitor of the neonatal Fc receptor (FcRn). In cynomolgus monkeys, single-dose intravenous (IV) or subcutaneous (SC) administration of BTL-203 produced deep and sustained reductions in total IgG. Using a semi-mechanistic FcRn–IgG turnover model calibrated to these data, subcutaneous administration every four weeks (Q4W) is projected to maintain clinically meaningful IgG suppression in humans and will be evaluated prospectively in clinical studies.
“These encouraging data, together with our translational modeling, indicate the potential for once-every-four-weeks subcutaneous dosing—less frequent than the weekly SC cycles and IV regimens used by currently approved FcRn therapies,” said Jiansong Yang, Ph.D., Chief Executive Officer of Biotle. “If confirmed clinically, this convenience alongside robust IgG lowering could position BTL-203 as a potential best-in-class therapy.”
Nonclinical highlights
- Robust IgG lowering vs comparator (IV): Single IV doses of BTL-203 (30 or 60 mg/kg) achieved higher systemic exposure and deeper, more-sustained IgG reductions than efgartigimod (48.5 mg/kg IV, in this cynomolgus study), with nadir IgG decreases of ~67–69% and recovery by ~4 weeks.
- SC administration: A single 15 mg/kg SC dose of BTL-203 yielded total-IgG reductions similar to efgartigimod 48.5 mg/kg IV in this model.
- Human projection: Population PK/PD modeling suggests Q4W SC dosing in humans could sustain IgG lowering within a therapeutic window; this projection will be tested in future clinical studies.
- Tolerability (monkey): BTL-203 15 mg/kg SC was well tolerated; albumin decreases and LDL-C changes were minimal and reversible.
Potential differentiation
Approved FcRn therapies for generalized myasthenia gravis (gMG) use weekly SC cycles (rozanolixizumab; efgartigimod + hyaluronidase) and IV regimens (efgartigimod IV weekly cycles; nipocalimab IV with q2w maintenance). If validated clinically, BTL-203’s Q4W SC profile would represent a less-frequent maintenance schedule within the class.
About BTL-203
BTL-203 is an FcRn inhibitor engineered for extended half-life to deliver deep IgG reduction with Q4W subcutaneous dosing. By blocking FcRn, BTL-203 accelerates IgG catabolism—a validated strategy across multiple IgG-mediated diseases. Biotle is advancing BTL-203 toward clinical development (IND submission planned Q2 2026) and is engaging potential partners to support global development and commercialization.
About Biotle
Biotle is a research-driven biotechnology company developing next-generation antibodies for oncology and autoimmune diseases, leveraging proprietary multispecific design to coordinate immune responses with a strong safety margin. For more information, visit www.biotle.com.
Forward-Looking Statements
This press release contains forward-looking statements, including statements regarding the potential safety, efficacy and clinical benefits of BTL-203, projected human dosing regimens, development plans and timelines, and potential partnering activities. Forward-looking statements are subject to risks and uncertainties that may cause actual results to differ materially, including preclinical-to-clinical translation risk, regulatory feedback, manufacturing and enrollment timelines, competitive developments, and other factors. Biotle undertakes no obligation to update these statements except as required by law.
Contacts
Business Development: bd@biotle.com