(M1430-02-06) Clinical Evidence of Safety, Prolonged Half-Life, and Low Immunogenicity of Monoclonal Antibodies TAVO101 and TAVO103 Engineered with Multiple Fc Mutations

Purpose: Engineering functional mutations in the Fc region of antibody-based therapeutics can enhance safety, extend circulation half-life, and improve in vitro and in vivo stabilities. While clinical data support half-life extension and modulation of the Fc effector functions, there is limited information regarding molecules incorporating multiple functional mutations. Additionally, no clinical safety and immunogenicity data have been reported for a protease resistance mutation in the human antibody IgG1 hinge area to improve stability, particularly in protease-rich disease conditions, such as inflammatory tissues. Moreover, protein engineers and clinicians seek more clinical data on fit-for-purpose antibodies with multiple functional mutations in the Fc region. We present clinical profiles of TAVO101 and TAVO103, IgG1-based anti-TSLP and anti-IL-1β antibodies (mAbs), respectively. These two antibodies were engineered to extend half-life and reduce Fc effector functions. In addition, TAVO103 has the protease-resistance modifications. Both molecules were evaluated in vitro and in clinical trials for safety, pharmacokinetics (PK), and immunogenicity.

Methods: TAVO101 and TAVO103 were engineered with the M428L/N434S (LS) mutations to extend their half-life, with the complementary L234A/L235A (LALA) mutations to silence Fc effector functions.  Additionally, TAVO103 included the E233P mutation and G236 deletion to improve hinge region protease resistance by disrupting the protease recognition sequences. Both molecules were produced for clinical trials using CHO cell expression systems and typical human mAb downstream processes. Binding affinities to FcRn at pH 6.0 were assessed using ELISA-based assays on a Maxisorp 96-well plate coated with recombinant FcRn protein. Binding to FcgRI (CD64), FcgRIIIA (CD16a), and C1q was evaluated on plates coated with recombinant human FcgRI, FcgRIIIA, or C1q proteins. The stability of the molecules against IgG protease IdeZ was tested at 37°C and analyzed using SDS-PAGE. First-in-human, double-blinded, single-dose escalation Phase 1 clinical studies were conducted in healthy volunteers in Australia (for TAVO101) and the US (for TAVO103) to assess the safety, PK profiles, and immunogenicity. Subjects received a single intravenous administration of the study drug or placebo, followed by a 195-day safety and PK assessment. Drug concentrations in serum samples were measured using validated specific ELISA-based assays. Anti-drug antibodies (ADA) were analyzed using screening and specificity assays, and the ADA titer in confirmed serum sample was measured. Treatment-emergent adverse events (TEAE) were coded using the System Organ Class (SOC) and Preferred Term (PT). Individual PK profiles were fitted into two-compartmental population models.

Results: In the FcRn binding assay, TAVO101 and TAVO103 showed approximately 5-fold and 2.7-fold increases in affinity at pH 6.0, respectively. The LALA mutations reduced the binding to FcgRI by about 18-70-fold, to FcgRIII by 5-10-fold and, eventually diminished C1q binding when compared to wild-type IgG1 isotypes. TAVO103 exhibited enhanced stability in the presence of IgG protease IdeZ, in comparison to the IgG1 wild-type or isotype with only LS and LALA mutations. In the clinical studies, both TAVO101 and TAVO103 were found to be safe and well-tolerated. The incidences and severities of treatment-emergent adverse events were mostly mild and comparable between the active and placebo groups. No severe adverse events, deaths, or treatment-related withdrawals were reported. For TAVO101, the adverse events assessed by the investigator and considered possibly related to the study drug included one event each of sleepiness, laryngitis, throat irritation, headache, thrombocytopenia, fatigue, dysgeusia, neutropenia, and running nose, all of which were recovered/resolved. All TAVO101-treated subjects tested negative for ADA (with 0 of 27 subjects testing positive). For TAVO103, the adverse events considered possibly related to the study drug were limited to 2 events of mild headache and 1 event each of mild dizziness and nausea, all of which were resolved within 5 days of onset. Only one subject tested positive with a low titer for ADA (1 of 20 subjects). The serum concentrations of both drugs separately fitted well in a two-compartment population PK model. The analyses revealed mean population clearances of 0.90 mL/day/kg for TAVO101 and 0.97 mL/day/kg for TAVO103, with half-lives of 64.5 and 56.8 days, respectively. The clearance was about 3-fold lower, and half-life was 3-fold longer than average wild-type IgG1 mAbs. These results were consistent with the median values obtained by noncompartmental analyses. Preliminary results from an ongoing Phase 2 study indicate that TAVO101 is efficacious in atopic dermatitis patients.

Conclusion: This study provides clinical evidence demonstrating the safety and effectively extended half-life of TAVO101 and TAVO103, both engineered with LS and LALA mutations. For the first time, clinical data confirm that TAVO103, which incorporated triple functional mutations for half-life extension, Fc silencing, and protease resistance, was safe and non-immunogenic in healthy subjects. These findings established a clinical proof-of-concept assessment on the combination of Fc functional mutations in IgG-based therapeutics and supported further evaluations in patient populations for therapeutic efficacy, safety, and immunogenicity.