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Monitoring guidance

Laboratory monitoring¹

Laboratory Measures	Monitoring guidance	Action
Platelet count	Before treatment initiation, 4 weeks after initiation, and thereafter according to routine patient management	Treatment should be discontinued if platelet count is <50 x 10³/mm³.
Lymphocyte	Before treatment initiation, 4 weeks after initiation, and thereafter according to routine patient management	Treatment should be interrupted if absolute lymphocyte count (ALC) is <0.5 x 10³/mm³ and may be restarted once ALC return above this value

Treatment initiation^₁
Treatment with Litfulo should not be initiated in patients with an absolute lymphocyte count <0.5 x 10³/mm³ or a platelet count <100x10³/mm³.

Haematologic abnormalities¹

	Lymphocyte counts	Platelet counts
*Placebo-controlled studies, for up to 24 weeks	Ritlecitinib was associated with decrease in lymphocyte counts Maximum effects on lymphocytes were observed within 4 weeks, after which lymphocyte count remained stable at a lower level with continued therapy.	Ritlecitinib was associated with decrease in platelet counts Maximum effects on platelets were observed within 4 weeks, after which platelet count remained stable at a lower level with continued therapy.
ALLEGRO 2b/3 up to 48 weeks
Integrated Safety Analysis	Confirmed ALC <0.5 × 10³/mm³ occurred in 3 participants (0.2%) treated with ritlecitinib 50mg.	2 patients (0.1%) treated with ritlecitinib 50mg or higher had a confirmed platelet count <100 × 10³/mm³.
Relevant monitoring actions	Prior to initiating treatment with Litfulo, ALC count should be performed. Treatment with Litfulo should not be initiated in patients with an ALC < 0.5 × 10³/mm³. ALC count is recommended at 4 weeks after initiation of therapy with Litfulo, and thereafter according to routine patient management. Litfulo should be interrupted if ALC is <0.5 × 10³/mm³and may be restarted once ALC returns above this value. There are limited data in patients ≥65 years of age. Age appeared to be a risk factor for lower level ALC in patients ≥65 years of age.	Prior to initiating treatment with Litfulo, platelet count should be performed. Treatment with Litfulo should not be initiated in patients with a platelet count < 100 × 10³/mm³. Platelet count is recommended at 4 weeks after initiation of therapy with Lifulo, and thereafter according to routine patient management. After initiating treatment with Litfulo, treatment interruption or discontinuation are recommended based on platelet count abnormalities. Litfulo should be discontinued if platelet count is <50 x 10³/mm³.

*Placebo-controlled studies in AA for up to 24 weeks included: ALLEGRO-2b/3 also known as AA-1.²

Creatine phosphokinase (CPK) and Transaminases Elevations¹

	Creatine phosphokinase (CPK)	Transaminases
Placebo-controlled studies, for up to 24 weeks	Ritlecitinib was associated with CPK elevations Events of blood CPK increased were reported in 2 patients (1.5%) treated with ritlecitinib 50mg. CPK elevations >5x ULN were reported in 5 (3.9%) of patients treated with ritlecitinib 50mg.	Ritlecitinib was associated with increased transaminases Events of increases in ALT and AST values (>3x ULN) were reported in 3 patients (0.9%) and 2 patients (0.6%) treated with ritlecitinib 50mg or higher, respectively. Most elevations were transient, and none led to discontinuation.
ALLEGRO 2b/3 up to 48 weeks	Events of blood CPK increased were reported in 3.8% of patients treated with ritlecitinib 50mg or higher CPK elevations >5x ULN were reported in 6.6% of patients treated with ritlecitinib 50mg or higher. Most elevations were transient, and none led to discontinuation.

Placebo-controlled studies in AA for up to 24 weeks included: ALLEGRO-2b/3 also known as AA-1.²

Clinically significant interactions with other medications¹
Potential for other medicinal products to affect the pharmacokinetics of ritlecitinib¹

The coadministration of multiple 200 mg doses of itraconazole, a strong CYP3A inhibitor, increased the area under curve (AUC)inf of ritlecitinib by approximately 15%. This is not considered clinically significant and, therefore dose adjustment is not required when ritlecitinib is coadministered with CYP3A inhibitors.

The coadministration of multiple 600 mg doses of rifampicin, a strong inducer of CYP enzymes, decreased the AUCinf of ritlecitinib by approximately 44%. This is not considered clinically significant and, therefore dose adjustment is not required when ritlecitinib is coadministered with inducers of CYP enzymes.

Clinically significant interactions with other medications¹
Potential for ritlecitinib to affect pharmacokinetics of other medications¹

Multiple doses of ritlecitinib 200mg increased the AUC_infand C_maxof midazolam, a CYP3A4 substrate, by approximately 2.7 fold and 1.8 fold, respectively. Ritlecitinib is a moderate inhibitor of CYP3A.

Caution should be exercised with concomitant use of ritlecitinib with CYP3A substrates (e.g. quinidine, ciclosporin, dihydroergotamine, ergotamine, pimozide) where moderate concentration changes may lead to serious adverse reactions.

Dose adjustment recommendations for the CYP3A substrate (e.g. colchicine, everolimus, tacrolimus, sirolimus) should be considered.

Multiple doses of ritlecitinib 200mg increased the AUCinf and Cmax of caffeine, a CYP1A2 substrate, by approximately 2.7 fold and 1.1 fold, respectively. Ritlecitinib is a moderate inhibitor of CYP1A2.

Caution should be exercised with concomitant use of ritlecitinib with other CYP1A2 substrates (e.g. tizanidine) where moderate concentration changes may lead to serious adverse reactions

Dose adjustment recommendations for the CYP1A2 substrate (e.g. theophylline, pirfenidone) should be considered.

Coadministration of a single ritlecitinib 400mg dose increased the AUC_infof sumatriptan, an OCT1 substrate, by approximately 1.3 to 1.5 fold, respectively, relative to sumatriptan given alone. The increase in sumatriptan exposure is not considered clinically relevant

Caution should be exercised with concomitant use of ritlecitinib with OCT1 substrates where small concentration changes may lead to serious adverse reactions

Ritlecitinib did not produce clinically significant changes in the exposures of oral contraceptives (e.g., ethinyl oestradiol or levonorgestrel), CYP2B6 substrates (e.g., efavirenz), CYP2C substrates (e.g., tolbutamide), or substrates of organic anion transporter (OAT)P1B1, breast cancer resistant protein (BCRP), and OAT3 (e.g., rosuvastatin).

Paediatric population¹
Interaction studies have only been performed in adults.

Immunosuppressive medicinal products¹
Combination with systemic immunosuppressive medicinal products has not been studied.

Concomitant use with ritlecitinib is not recommended as a risk of additive immunosuppression cannot be excluded.

ALT=alanine transaminase; AST=aspartate aminotransferase; CPK=creatine phosphokinase; ULN=upper limit of normal: AUC_inf=area under curve to infinity: C_max=maximum concentration: CYP=cytochrome P450: OCT=organic cation transporter: PK=pharmacokinetics

Please refer to the Litfulo Summary of Product Characteristics for further information.

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References:
1. Litfulo (ritlecitinib) Summary of Product Characteristics
2. King B, Zhang X, Harcha WG, et al. Lancet.2023 May 6;401(10387):1518-1529.

PP-LGF-GBR-0272. July 2025

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