IBAT inhibitors | gutsandgrowth

This blog entry has abbreviated/summarized this presentation. Though not intentional, some important material is likely to have been omitted; in addition, transcription errors are possible as well. Another great lecture from Dr. Suchy.

IBAT Inhibitors Frederick Suchy

Key points:

IBAT inhibitors block intestinal absorption of bile acids/disrupt enterohepatic circulation; this leads to augmented bile acid excretion in stools
IBAT inhibitors may reduce liver damage in the setting of cholestasis/accumulation of toxic bile acids
Potential diseases for IBAT inhibitors include Alagille syndrome and PFIC
Van Wessel et al (J Hepatol 2020; 73: 84-93) correlated survival with PFIC1/PFIC2 with bile acid levels and showed improvement in survival in those with surgical biliary diversion
Goals for IBAT inhibitor trials: improvement in pruritus, bile acids, reduced ALT, hepatic fibrosis, HCC and need for liver transplantation
Marixibat is available for use as an FDA approved breakthrough medication for Alagille and PFIC2 in pediatric patients older than 1 year
Odexibat is designated as an orphan drug for Alagille, PFIC, PBC, and biliary atresia
Safety appears good with IBAT inhibitors. Fat soluble vitamin monitoring is needed

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Related blog posts:

Case report: Alejandro Velez Lopez

3 yo presented with fatigue and jaundice, 3 weeks after COVID-19 infection. She was not taking any medications. Labs: ALT 939, AST 1321, T bili 5.5, D bili 0.9, INR 2, Plts 174, Hgb 12.8, LDH 1297. remained positive for SARS-CoV2 by PCR. Acetaminophen -no exposure. Evaluation: LKM 1:1280. Neg ANA, NL Ferritin, NL sIL2r, Other viral studies negative, NL IgG. Developed encephalopathy with NH4 317, INR peaked at 2.8. Treated with steroids, rifaximin and lactulose. Liver biopsy showed sub-massive necrosis and fibrosis (indicative of autoimmune hepatitis, likely triggered or exacerbated by COVID-19). Patient responded to medical therapy and did not require liver transplantation.

A great and short webinar was recently presented from the NASPGHAN Foundation with three lectures

Webinar: Alagille Syndrome (If this link does not work, the On Demand version of the webinar is now available on LearnOnLine, at https://learnonline.naspghan.org/products/on-demand-advances-in-diagnosis-and-treatment-of-alagille-syndrome. You can also find it by logging into LearnOnline at https://learnonline.naspghan.org/ and entering the Webinars section.)

The first lecture by Dr. Melissa Gilbert was an excellent overview of the genetics of Alagille Syndrome.

Key points:

JAG1 mutations account for ~95% of Alagille syndrome mutations and NOTCH2 about 3%
Many mutations identified are due to missense mutations which are often variants of unknown clinical significance (VOUS). In these patients, to determine if it is pathogenic, one has to correlate the clinical picture along with specific amino acid change, location of variant, and frequency of variant in normal population. Dr. Gilbert noted that among the ~97% of cases with genetic abnormalities, about 80% have recognized pathogenic mutations and about 17% have VOUS.
There is variability of severity of Alagille syndrome in the same family, likely related to genetic modifiers
When using genetic panel, if panel uses only single nucleotide variants, this will miss the deletion/duplication variants which account for ~10% of cases

The second lecture by Binita Kamath was a terrific review and compared the differences between Alagille Syndrome with JAG1 mutations and NOTCH2; the latter are much less likely to have cardiac abnormalities and butterfly vertebrae. The liver phenotype/survival is similar.

Key points:

Outcomes of Alagille syndrome by 25 years of age including frequent bone fractures and development of portal hypertension.
Severe liver disease is common. 75% in a multi-center cohort (CHILDREN) required liver transplantation by age 18 years and 10% died; in contrast, a large GALA cohort of 911 children, 41% survived with their native liver at 18 years.
After transplantation, renal sparing strategies are needed due to frequent renal insufficiency; patients with severe cardiac disease may not be candidates for liver transplantation.
There is work on an Alagille Syndrome growth curve.
Screening for brain vascular malformations/Moyamoya –Dr. Kamath tends to screen after age 8 years of age at baseline (when child does not need sedation for brain imaging) and then every 4-5 years. Also, an MRI/MRA is done prior to major surgery.
Hyperlipidemia in Alagille Syndrome is mainly due to lipoprotein X; this is not a risk factor for cardiac health.

The third (& also excellent) lecture by Saul Karpen (who disclosed his potential conflicts of interest) reviewed current treatments and emerging treatments.

Key points:

The current medical therapies have not been carefully tested; rifampin for pruritus may relieve cholestasis in about 50% of patients.
IBAT inhibitors interrupt enterohepatic circulation. These agents improve pruritus and decrease serum bile acids.
Dr. Karpen reminded the audience to follow fat soluble vitamin levels and if treatment is needed, to provide Vitamin D formulations with TPGS.