Tenofovir Alafenamide

證據等級: L5

預測適應症: 3 個

Tenofovir Alafenamide: From HIV-1 Infection to Simian Immunodeficiency Virus (SIV) Infection

One-Sentence Summary

Tenofovir alafenamide (TAF) is a nucleotide reverse-transcriptase inhibitor prodrug whose established clinical role is HIV-1 treatment and pre-exposure prophylaxis (PrEP); no original-indication record exists in this evidence pack because the drug is not marketed in Taiwan. TxGNN's top scored prediction, Simian Immunodeficiency Virus (SIV) infection, is supported only by 1 tangentially relevant clinical trial and 9 non-human-primate (NHP) preclinical publications — no human efficacy data exist for this specific indication. Two other candidates in this pack (feline AIDS, and a rare neurodevelopmental disorder) carry zero supporting evidence and/or fall outside human-drug repurposing scope, so they are noted but not developed further below.

Quick Overview

Item	Content
Original Indication	Not documented in this evidence pack (no Taiwan licenses on file); TAF is internationally established as an antiretroviral for HIV-1 infection/PrEP
Predicted New Indication	Simian Immunodeficiency Virus (SIV) Infection
TxGNN Prediction Score	99.89%
Evidence Level	L4 (preclinical/NHP challenge-model evidence only; no completed human RCT or observational study specific to this indication)
Taiwan Market Status	Not marketed
Number of Authorizations	0
Recommended Decision	Hold

Why is This Prediction Reasonable?

Detailed mechanism-of-action data for TAF is not available in this evidence pack (flagged as data gap DG002). Based on known pharmacology, TAF is a prodrug that is intracellularly converted to tenofovir diphosphate, which inhibits retroviral reverse transcriptase — the same enzyme class targeted in HIV-1 treatment.

SIV is a lentivirus closely related to HIV-1 and infects non-human primates; because the two viruses share reverse-transcriptase biology, TAF's antiviral mechanism is plausible in the SIV/SHIV (simian-human immunodeficiency virus) macaque model. However, the supporting literature is almost entirely translational research designed to validate TAF as PrEP/PEP for human HIV prevention using SIV/SHIV-infected macaques as a surrogate model — it is not evidence that TAF treats SIV infection as a disease in its own right. SIV infection itself is a veterinary/research-model condition, not a human clinical indication, which limits the practical repurposing value of this prediction despite the high TxGNN similarity score.

For context, the other two TxGNN candidates in this pack are weaker still: feline acquired immunodeficiency syndrome is an explicitly veterinary indication outside the company's human-drug repurposing scope, and the rare neurodevelopmental disorder has no clinical, preclinical, or mechanistic support whatsoever (pure embedding-similarity prediction, L5).

Clinical Trial Evidence

Trial Number	Phase	Status	Enrollment	Key Findings
NCT03577782	Phase 1/2	Unknown	12	Trial of vedolizumab + antiretroviral therapy aiming for virologic remission in HIV-infected subjects; TAF is only incidentally part of background ART, and the trial does not target SIV infection directly (relevance grade C)

Literature Evidence

PMID	Year	Type	Journal	Key Findings
39632836	2024	Preclinical (SHIV remission, macaque)	Nature Communications	Oral emtricitabine/TAF plus long-acting cabotegravir/rilpivirine tested for SHIV remission in macaques
38134382	2024	Preclinical (NHP model)	J Infect Dis	TAF/elvitegravir vaginal inserts gave 93–100% protection against repeated SHIV vaginal exposure in macaques
39559349	2024	Preclinical (humanized mouse model)	Frontiers in Immunology	Dual-purpose humanized mouse model proposed for testing antiviral strategies against SIV and HIV
35913838	2022	Preclinical (implant device, NHP)	J Antimicrob Chemother	Biodegradable TAF-releasing implant evaluated for sustained vaginal HIV/SHIV protection in macaques
31362305	2019	Preclinical (macaque efficacy)	J Infect Dis	Oral TAF/emtricitabine or TAF alone tested against vaginal SHIV infection in macaques (PrEP model)
31730629	2019	Preclinical (methodology, macaque)	PLoS One	Protocol for daily oral ARV dosing in macaques to improve compliance in SIV/SHIV prevention studies
27465645	2016	Preclinical (macaque chemoprophylaxis)	J Infect Dis	Oral TAF/emtricitabine prevented rectal SHIV infection in macaques
22740713	2012	Preclinical (SHIV, macaque)	J Infect Dis	Oral PrEP reduced inflammation and CD4 loss in acute SHIV infection
16810108	2006	Preclinical (infant macaque)	J Acquir Immune Defic Syndr	Oral tenofovir DF and topical GS-7340 (TAF precursor) evaluated against oral SIV challenge in infant macaques

Taiwan Market Information

Currently no Taiwan marketing authorizations on file (0 licenses; market status: not marketed).

Safety Considerations

Please refer to the package insert for safety information. (No warnings, contraindications, or drug-interaction data were retrievable in this cycle — see data gap DG001, marked Blocking.)

Conclusion and Next Steps

Decision: Hold

Rationale: All available evidence for the top prediction (SIV infection) is preclinical NHP model data supporting TAF as HIV prevention/PrEP in humans, not evidence of efficacy for treating SIV infection as a standalone indication; SIV infection is itself an animal/research-model disease rather than a human clinical target. Combined with the absence of TFDA safety/label data (Blocking gap) and MOA data, this candidate set does not currently support progression.

To proceed, the following is needed:

TFDA package insert (warnings/contraindications) — Blocking gap, required before any S1 safety review
DrugBank-sourced mechanism-of-action data to properly assess mechanistic fit
Re-evaluation of whether SIV infection should be reframed as a human indication (e.g., HIV-1 PrEP/treatment) rather than pursued literally, since the current disease label is not a viable human repurposing target
If pursuing further, deprioritize the feline AIDS (veterinary, out of scope) and neurodevelopmental-disorder (L5, no evidence) candidates from this set
Disclaimer

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