Givosiran

Evidence Level: L5

Predicted Indications: 10

Givosiran
Givosiran: From Acute Hepatic Porphyria to Porphyria Due to ALA Dehydratase Deficiency

## Pharmacist Assessment Report

Givosiran: From Acute Hepatic Porphyria to Porphyria Due to ALA Dehydratase Deficiency

One-Sentence Summary

Givosiran is a hepatocyte-targeted siRNA originally approved for acute hepatic porphyria (AHP), a group of four inherited disorders of heme biosynthesis. TxGNN’s two highest-scoring predictions for this drug (hepatopulmonary syndrome, portal hypertension variants, hepatitis B/C, etc.) are flagged in the evidence pack itself as mechanistically implausible — likely a knowledge-graph embedding artifact around “liver-targeted drugs” rather than a real signal, with zero supporting trials or literature. The one candidate with genuine evidence is porphyria due to ALA dehydratase deficiency (ADP), which is actually one of the four AHP subtypes already covered by Givosiran’s approved label; 8 publications support this pathway, but they include one case report of clinical non-response, so this is presented as an evidence review of an existing label subtype rather than a novel repurposing opportunity.

Note on candidate selection: This report deviates from TxGNN’s #1-ranked prediction (rank 1, score 99.999%) because the evidence pack’s own repurposing_rationale explicitly states there is “no mechanistic link” for ranks 1–8 and rank 10 — hepatopulmonary syndrome, portal hypertension/vascular liver diseases, viral hepatitis, and metabolic disorders unrelated to heme biosynthesis. Reporting on that top score would be misleading. Rank 9 (ALA dehydratase deficiency porphyria) is the only candidate with real literature evidence and a coherent mechanism, so it is used here instead.

Quick Overview

Item	Content
Original Indication	Acute hepatic porphyria (AHP) — per literature; not present in structured `taiwan_regulatory` data
Predicted New Indication	Porphyria due to ALA dehydratase deficiency (ADP)
TxGNN Prediction Score	99.91% (rank 1286 of all predictions)
Evidence Level	L3 (observational studies + Phase 3 post-hoc analysis for AHP broadly; only a single case report is specific to ADP)
Taiwan Market Status	Not marketed (Not marketed)
Number of Authorizations	0
Recommended Decision	Hold

Why is This Prediction Reasonable?

original_moa is marked as a data gap in the structured record, but the literature evidence retrieved for this candidate independently describes the mechanism: Givosiran is a GalNAc-conjugated siRNA that is taken up by hepatocytes and targets ALAS1 mRNA, silencing hepatic ALA synthase 1. This blocks the upstream, rate-limiting step of heme biosynthesis and prevents accumulation of the neurotoxic intermediates δ-aminolevulinic acid (ALA) and porphobilinogen (PBG) that drive acute porphyria attacks.

Acute hepatic porphyria (AHP) is not a single disease but an umbrella of four enzyme deficiencies in the heme pathway: acute intermittent porphyria, hereditary coproporphyria, variegate porphyria, and ALA dehydratase deficiency porphyria (ADP). Because all four share the same downstream toxic-metabolite mechanism, ADP is already within Givosiran’s approved regulatory indication for AHP — this is not really a novel “repurposing” candidate in the TxGNN sense, but an ultra-rare subtype for which disease-specific clinical evidence is sparse.

Critically, one published case report (PMID 35991568) documents a patient with genetically confirmed ADP who did not respond clinically to Givosiran despite the shared mechanism, illustrating that mechanistic plausibility does not guarantee subtype-level efficacy. This tempers the otherwise strong mechanistic rationale and is the main reason this evaluation does not support a “Go” recommendation.

Clinical Trial Evidence

Currently no related clinical trials registered specific to porphyria due to ALA dehydratase deficiency. (The evidence pack references the Phase 3 ENVISION trial only indirectly, via a post-hoc literature analysis — see Literature Evidence below — not as a registered trial record for this candidate.)

Literature Evidence

PMID	Year	Type	Journal	Key Findings
36028858	2022	Phase 3 RCT (post-hoc analysis)	Orphanet Journal of Rare Diseases	Post-hoc analysis of the Phase 3 ENVISION trial quantifying AHP disease burden in patients ≥12 years treated with givosiran
40312531	2025	Observational (expanded access study)	Scientific Reports	Open-label, single-arm study in 10 Japanese AHP patients on monthly subcutaneous givosiran (2.5 mg/kg); reports safety/efficacy in expanded access setting
35067977	2022	Observational	Journal of Internal Medicine	RNAi therapy with givosiran significantly reduces attack rates in acute intermittent porphyria
35734365	2022	Review	Drug Design, Development and Therapy	Overview of givosiran’s design, development, and therapeutic place for adults with AHP
39313028	2024	Review	Revista Clínica Española	Therapeutic approach to acute crises of hepatic porphyria, covering ALAD deficiency as a subtype triggered by hepatic ALAS1 induction
37027823	2023	Review	Blood	Review of RNA interference therapy mechanism and clinical use across the four AHP subtypes
36883675	2023	PK/PD modeling study	CPT: Pharmacometrics & Systems Pharmacology	Pharmacokinetic-pharmacodynamic model of urinary ALA reduction after givosiran treatment, pooled from Phase I–III trials
35991568	2022	Case report	Frontiers in Genetics	Disease-specific evidence: documented lack of clinical response to givosiran in a genetically confirmed case of ALAD porphyria, despite approval covering this subtype

Taiwan Market Information

Givosiran currently holds 0 authorizations in the Taiwan regulatory dataset (market_status: Not marketed / not marketed). No license records are available to summarize dosage form or approved indication text.

Safety Considerations

Please refer to the SmPC for safety information. (Key warnings, contraindications, and DDI data are all unavailable in the current evidence pack — this is flagged as a Blocking data gap, see Conclusion.)

Conclusion and Next Steps

Decision: Hold

Rationale:

The mechanistic rationale is sound (ADP shares Givosiran’s ALAS1-silencing mechanism with the already-approved AHP indication), but the only disease-specific real-world evidence is a single case report showing treatment failure, and no dedicated controlled trial exists for this subtype.
Taiwan-specific regulatory data (label, warnings, contraindications) is entirely absent — this is a Blocking data gap (DG001) that prevents any safety pre-assessment regardless of efficacy evidence.
TxGNN’s higher-scoring predictions for this drug (ranks 1–8, 10) were reviewed and excluded as mechanistically unsupported per the evidence pack’s own annotations, leaving no stronger candidate to promote instead.

To proceed, the following is needed:

TFDA/SmPC label data (warnings, contraindications) — currently blocking (DG001)
Confirmed original MOA documentation from DrugBank (DG002)
Additional ADP-specific case series or registry data to reconcile the conflicting response signal (one negative case vs. mechanistic plausibility)
Clarification of whether this candidate should be tracked as “new indication” or “known label subtype with evidence gap,” since ADP is not truly outside Givosiran’s current approved use
Disclaimer

This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.