Ritlecitinib (Litfulo)
First oral JAK3/TEC selective inhibitor FDA-approved for alopecia areata
About This Treatment
Ritlecitinib is a highly selective inhibitor of JAK3 and TEC family kinases, the first oral JAK-selective inhibitor approved by FDA (2023) for alopecia areata treatment. JAK3 is expressed predominantly in lymphocytes (T cells, NK cells, B cells), achieving more selective immunosuppression than baricitinib's pan-JAK1/2 inhibition. It specifically blocks JAK3-dependent Th1/Tc1 cell differentiation, the fundamental cause of autoimmune T cell infiltration in alopecia areata, suppressing autoimmune hair follicle attack and promoting hair regeneration.
Mechanism of Action
Ritlecitinib is highly selective for JAK3 and TEC family kinases (ITK, BTK). JAK3 particularly involves IL-2R (T cell receptor signaling) and IL-7R (T cell survival signaling); blocking these signals suppresses Th1 and cytotoxic T cell (Tc1) differentiation. ITK directly suppresses IFN-γ production from Th1 cells, while BTK suppresses B cell activation. In alopecia areata, hair follicle-specific autoreactive T cells (anti-hair matrix CD8+ T cells) are reduced, restoring follicle immune privilege and promoting hair regeneration. Unlike pan-JAK1/2 inhibition, more selective immunosuppression with improved safety is expected.
Indications
Expected Results
Hair regrowth initiated 8-12 weeks after initial treatment; ~60-70% of patients achieve >80% scalp coverage by 6 months. Particularly for totalis/universalis forms, higher hair regrowth rates expected compared to baricitinib.
Clinical Evidence
Risks & Side Effects
Infection risk expected lower than baricitinib; lipid and CPK elevations reported limited. Headache and upper respiratory infections reported. Avoid in patients planning pregnancy. Long-term safety data still accumulating.
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