Shares in Roivant Sciences' Immunovant shot up over 90% on Tuesday after the company disclosed positive results from a Phase I trial of its neonatal FcRn inhibitor IMVT-1402 for autoimmune disease. The data support a "best-case scenario," noted Truist Securities analyst Robyn Karnauskas, suggesting that the drug has the potential to be the best in its class.The randomised, placebo-controlled trial is evaluating safety, tolerability, pharmacokinetics and pharmacodynamics of single- (SAD) and multiple-ascending doses (MAD) of IMVT-1402 in healthy adults. In the SAD portion of the study, Immunovant said subcutaneously administered IMVT-1402 showed a "consistent reduction in IgG with potency that was similar to or greater than" that of its other experimental treatment, batoclimab.That drug, codenamed IMVT-1401, is a monoclonal antibody directed against FcRn as well, and is in Phase III development for myasthenia gravis and thyroid-eye disease. It is also in mid-stage testing for chronic inflammatory demyelinating polyneuropathy (CIDP) and Graves' disease. However, batoclimab has been associated with increases of LDL-cholesterol, which led to a pause of studies in 2021. Immunovant said Tuesday that there were no significant increases from baseline in LDL-C, or reductions in serum albumin, in the SAD portion of the IMVT-1402 trial.Reduction in inflammation-causing antibodyMeanwhile, Immunovant also reported initial MAD study results for the subcutaneous 300mg cohort of IMVT-1402 ahead of schedule. Those early-stage data were originally expected in October or November. The company said that after four weekly doses, the mean total IgG reduction from baseline was 63% in this cohort, with no decrease observed in serum albumin below baseline, or increase in LDL-C above baseline. Treatment-emergent adverse events were either mild or moderate in severity. Dosing for the 600mg cohort recently got under way."These first-in-human results are consistent with those observed in prior non-human primate studies, and we look forward to sharing additional MAD data in November," stated CEO Pete Salzmann. Jefferies analyst Dennis Ding suggested the positive early readout from IMVT-1402 could give Roivant another "potentially blockbuster" candidate to transact, after the readout for its Pfizer-partnered ulcerative colitis treatment RVT-3101 earlier this year.Johnson & Johnson, argenx and UCB are also developing treatments belonging to the neonatal FcRn inhibitor class. In a note to clients last month, H.C. Wainwright & Co. viewed the Phase I readout as an "important catalyst" for Immunovant, possibly setting up Phase II studies for IMVT-1402 next year. They suggested the focus is not on efficacy because batoclimab has already demonstrated "robust efficacy" in reducing IgG levels, but that the Phase I readout "is of more significance than usual, as we will get an answer on a potential effect of IMVT-1402 on albumin and LDL."As for batoclimab, the analysts anticipate Phase II data in Graves' disease by year-end, as well as top-line results from the Phase III trial in myasthenia gravis and initial findings from the Phase IIb trial in CIDP in 2024. "We believe these two trials have high probability of success, as the mechanism of action has been validated by other anti-FcRn manufacturers, most recently argenx in CIDP," they said. Top-line data from the Phase III programme in thyroid-eye disease are due in 2025, with the analysts saying Immunovant has a "competitive advantage over argenx," whose registrational study in this indication is anticipated to start in the fourth quarter of 2023.Roivant, a controlling holder in Immunovant, had planned to buy the remaining stake in the company in 2021, but instead, later put up a $200-million investment to help advance the development of batoclimab in multiple indications.