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Important Safety Information

Warnings and Precautions:

Liver Test Abnormalities

Patients enrolled in a clinical trial had abnormal liver tests at baseline. In a clinical trial, treatment-emergent elevations of liver tests or worsening of liver tests relative to baseline values were observed during the clinical trial. Most abnormalitiesincluded elevation in AST, ALT, or total and direct bilirubin. Treatment interruption days ranged from 3 days to 124 days; none of the patients in the pivotal clinical trial permanently discontinued treatment due to liver test abnormalities.

Obtain baseline liver tests and monitor during treatment. Dose reduction or treatment interruption may be required if abnormalities occur. For persistent or recurrent liver test abnormalities, consider treatment discontinuation.

Bylvay was not evaluated in PFIC patients with cirrhosis. Closely monitor for liver test abnormalities; permanently discontinue Bylvay if a patient progresses to portal hypertension or experiences a hepatic decompensation event.


In a clinical trial, diarrhea was reported in 2 (10%) placebo-treated patients, 9 (39%) Bylvay-treated 40 mcg/kg/day patients and 4 (21%) Bylvay-treated 120 mcg/kg/day patients. Treatment interruption due to diarrhea, occurred in 2 patients with 3 eventsduring treatment with Bylvay 120 mcg/kg/day. Treatment interruption due to diarrhea ranged between 3 to 7 days. One patient treated with Bylvay 120 mcg/kg/day withdrew from the pivotal clinical trial due to persistent diarrhea.

If diarrhea occurs, monitor for dehydration and treat promptly. Interrupt Bylvay dosing if a patient experiences persistent diarrhea. Restart Bylvay at 40 mcg/kg/day when diarrhea resolves, and increase the dose as tolerated if appropriate. If diarrheapersists and no alternate etiology is identified, stop Bylvay treatment..

Fat-Soluble Vitamin (FSV) Deficiency

Fat-soluble vitamins (FSV) include vitamin A, D, E, and K (measured using INR levels). PFIC patients can have FSV deficiency at baseline. Bylvay may affect absorption of fat-soluble vitamins. In a clinical trial, new onset or worsening of existing FSVdeficiency was reported in 1 (5%) placebo-treated patient, and 3 (16%) Bylvay-treated 120 mcg/kg/day patients; none of the Bylvay-treated 40 mcg/kg/day patients had new onset or worsening of existing FSV deficiency.

Obtain serum FSV levels at baseline and monitor during treatment, along with any clinical manifestations. If FSV deficiency is diagnosed, supplement with FSV. Discontinue Bylvay if FSV deficiency persists or worsens despite adequate FSV supplementation.

Adverse Reactions

The most common adverse reactions for Bylvay are diarrhea, liver test abnormalities, vomiting, abdominal pain, and fat-soluble vitamin deficiency.

Drug Interactions

For patients taking bile acid binding resins, take Bylvay at least 4 hours before or 4 hours after taking a bile acid binding resin.

Use in Specific Populations

There are no human data on Bylvay use in pregnant persons to establish a drug-associated risk of major birth defects, miscarriage, or adverse developmental outcomes. Based on findings from animal reproduction studies, Bylvay may cause cardiac malformationswhen a fetus is exposed during pregnancy.

Indication and Usage

Bylvay is an ileal bile acid transporter (IBAT) inhibitor indicated for the treatment of pruritus in patients 3 months of age and older with progressive familial intrahepatic cholestasis (PFIC).

Limitation of Use:

Bylvay may not be effective in PFIC type 2 patients with ABCB11 variants resulting in non-functional or complete absence of bile salt export pump protein (BSEP-3).