Emtricitabine
| Evidence Level: L4 | Predicted Indications: 3 |
Table of Contents
Emtricitabine: From HIV-1 Infection to Simian Immunodeficiency Virus Infection
One-Sentence Summary
Emtricitabine is a nucleoside reverse transcriptase inhibitor, a class used against HIV-1, and the record’s approved-indication text is empty. The TxGNN model predicts it may be effective for simian immunodeficiency virus (SIV) infection, a non-human primate disease that mainly serves as a preclinical model of HIV. Support is weak: 2 clinical trials (both graded C, neither showing emtricitabine efficacy in SIV) and 20 publications, almost all macaque animal studies.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | HIV-1 infection (general class knowledge; the approved-indication text in the record is empty) |
| Predicted New Indication | Simian immunodeficiency virus infection |
| TxGNN Prediction Score | 99.92% |
| Evidence Level | L4 |
| US Market Status | ✓ Marketed |
| Number of NDAs | 20 |
| Recommended Decision | Hold |
Why is This Prediction Reasonable?
Currently, detailed mechanism of action data is not available in the record. Based on known class information, emtricitabine is a cytidine nucleoside reverse transcriptase inhibitor. Its triphosphate metabolite competes with dCTP and terminates the growing proviral DNA chain.
SIV’s reverse transcriptase is closely related to that of HIV-1. A drug that blocks HIV-1 replication is therefore expected to act on SIV as well. The macaque studies below support this: emtricitabine, usually combined with tenofovir, has been tested extensively against SIV and SHIV (a chimeric SIV/HIV virus) in prophylaxis and treatment models.
SIV infects non-human primates, so this prediction is a preclinical model signal. It is not a new human repurposing indication. Emtricitabine’s human counterpart, HIV-1, is already a labelled use, and the record’s empty indication field does not capture it.
Clinical Trial Evidence
| Trial Number | Phase | Status | Enrollment | Key Findings |
|---|---|---|---|---|
| NCT00863668 | NA | Withdrawn | 0 | HIV-1 decay kinetics with raltegravir. Not SIV, no participants enrolled, and emtricitabine involvement is not shown. Relevance grade C. |
| NCT03577782 | Phase 1/2 | Unknown | 12 | Vedolizumab plus antiretroviral therapy in HIV-infected subjects. Not SIV, and emtricitabine is not confirmed as part of the regimen. Relevance grade C. |
Literature Evidence
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 20874040 | 2010 | Review | Pharmacotherapy | Reviews systemic pre-exposure prophylaxis for HIV as a way to reduce transmission in at-risk people. |
| 22964889 | 2012 | Review | Curr Opin HIV AIDS | Reviews lessons from animal models of antiretroviral prophylaxis and next steps in preclinical PrEP research. |
| 31362305 | 2019 | Animal study (macaque) | J Infect Dis | Tested whether oral tenofovir alafenamide (TAF) alone or with emtricitabine prevents vaginal SHIV infection in macaques. |
| 29788316 | 2018 | Animal study (macaque) | J Infect Dis | Tested whether a vaginal emtricitabine/tenofovir gel also protects against repeated rectal SHIV exposures. |
| 27465645 | 2016 | Animal study (macaque) | J Infect Dis | Oral emtricitabine plus TAF protected macaques from rectal SHIV infection. |
| 26743846 | 2016 | Animal study (macaque) | J Infect Dis | Emtricitabine/tenofovir disoproxil fumarate (TDF) prevented vaginal SHIV infection in macaques coinfected with Chlamydia trachomatis and Trichomonas vaginalis. |
| 23633402 | 2013 | Animal study (macaque) | J Infect Dis | Evaluated oral emtricitabine/TDF against a tenofovir-resistant (K65R) SHIV in macaques (6 treated vs 6 untreated). |
| 22814162 | 2012 | Animal study (macaque) | Jpn J Infect Dis | Double oral dosing of emtricitabine/tenofovir before exposure protected against highly pathogenic SHIV in macaques. |
| 21632769 | 2011 | Animal study (macaque) | J Virol | Intermittent Truvada protected against rectal transmission of an emtricitabine-resistant (M184V) SHIV. |
| 12021341 | 2002 | Animal study (macaque) | J Virol | In SIVmac251-infected newborn macaques treated with lamivudine or emtricitabine, M184V resistance mutants emerged within 5 weeks. |
US Market Information
The record lists 20 authorizations in total, and its approved-indication text is empty for all of them. The five main entries:
| Authorization Number | Product Name | Dosage Form | Manufacturer |
|---|---|---|---|
| NDA 021500 | Emtriva | Capsule | Gilead Sciences, Inc. |
| ANDA 091168 | emtricitabine | Capsule | Cipla USA Inc. |
| ANDA 079188 | Emtricitabine | Capsule | Aurobindo Pharma Limited |
| NDA 021896 | Emtriva | Solution | Gilead Sciences, Inc. |
| ANDA 212114 | Emtricitabine and Tenofovir Disoproxil Fumarate | Film-coated tablet | Major Pharmaceuticals |
Safety Considerations
Please refer to the package insert for safety information.
Conclusion and Next Steps
Decision: Hold
Rationale: The mechanism is plausible and macaque studies support it, but the evidence is preclinical only (L4). Both retrieved trials are HIV-1 studies with no emtricitabine efficacy data in SIV. SIV is a non-human primate pathogen, so this is not a human repurposing indication.
To proceed, the following is needed:
- Package insert warnings and contraindications (a blocking gap for safety screening)
- Mechanism of action data from DrugBank
- A corrected original-indication record (HIV-1 infection) so the prediction is not read as a new human use
- A decision on whether SIV or SHIV macaque models are a meaningful development target, or whether this candidate should be closed as a model-organism artifact
- Direct SIV-specific studies of emtricitabine, since most of the current literature uses SHIV
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.