Vaccine Info

Tembexa Oral Antiviral

Authored by
Last reviewed
September 27, 2022
Fact checked by
Robert Carlson, MD

Tembexa® Oral Antiviral Description

Tembexa® (brincidofovir) is an oral antiviral approved by the U.S. Food and Drug Administration (FDA) in June 2021, in tablet and oral suspension formulations, for treating smallpox disease in adult and pediatric patients. Tembexa was developed with the U.S. Department of HHS’ Biomedical Advanced Research and Development Authority (BARDA). The initial U.S. Approval was in 1996. In addition, Tembexa received U.S. FDA Priority Review, Fast Track, and Orphan Drug designations. 

Brincidofovir is an orthopoxvirus nucleotide analog DNA polymerase inhibitor and a lipid conjugate of the nucleotide analog cidofovir and is indicated for treating human smallpox disease. The full chemical name is: Phosphonic acid, P-[[(1S)-2-(4-amino-2-oxo-1(2H)-pyrimidinyl)-1- (hydroxymethyl)ethoxy]methyl]-, mono[3-(hexadecyloxy)propyl] ester.

Chimerix is a biopharmaceutical company located in North Carolina with a mission to develop medicines that meaningfully improve and extend the lives of patients facing deadly diseases.

Emergent BioSolutions Inc. (NYSE: EBS) acquired the exclusive worldwide rights to TEMBEXA on September 26, 2022.

Tembexa Indication

Tembexa is a medical countermeasure recently approved for treating smallpox in all age groups, including infants and patients with difficulty swallowing. According to the U.S. CDC, the variola virus is ranked in the highest risk category for bioterrorism agents (Category A) due to its ease of transmission, high mortality rate, and potential to cause public panic and social disruption.

TEMBEXA should not be co-administered with intravenous cidofovir.

Tembexa Dosage

TEMBEXA is an oral antiviral formulated as 100 mg tablets and 10 mg/mL oral suspension dosed once weekly for two weeks. Tembexa is available in both tablets and oral suspension. It was the first antiviral to be approved for the treatment of smallpox in all age groups, including infants and patients with difficulty swallowing.

Tembexa Preparation

Tembexa is considered a potential human carcinogen. Therefore, do not crush or divide Tembexa tablets and avoid direct contact with broken or crushed tablets or oral suspension.

Tembexa Side Effects

BOXED WARNING: An increased incidence of mortality was seen in TEMBEXA-treated subjects compared to placebo-treated subjects in a 24-week clinical trial when TEMBEXA was evaluated in another disease. Therefore, safety information to support approval of Tembexa was derived from clinical trials of the drug for a non-smallpox indication, primarily from patients who received hematopoietic stem cell transplants. The following clinically significant adverse reactions: Elevations in hepatic transaminases and bilirubin; Diarrhea; and other GI adverse events.

Common adverse reactions (adverse events assessed as causally related by the investigator in ≥ 2% of subjects) experienced in the first two weeks of dosing with TEMBEXA were diarrhea, nausea, vomiting, and abdominal pain.

Patients are encouraged to report the adverse side effects of prescription drugs to the FDA. Visit or call 1-800-FDA-1088.

Tembexa Fertility

Male Infertility: Based on testicular toxicity in animal studies, Tembexa may irreversibly impair fertility in individuals of reproductive potential.

Based on findings from animal reproduction studies, TEMBEXA may cause fetal harm when administered to pregnant individuals. Pregnancy testing should be performed before initiation of TEMBEXA in individuals of childbearing potential to inform risk. An alternative therapy should be used to treat smallpox during pregnancy, if feasible.

Tembexa U.S. Government Contract

The 10-year contract (75A50122C00047), valued at up to $680 million, to supply up to 1.7 million treatment courses of tablet and suspension formulations of TEMBEXA® to the U.S. government, was awarded to Chimerix on August 29, 2022. The contract includes an initial product procurement valued at approximately $115 million, with optional future procurement valued at up to approximately $551 million, exercisable at the sole discretion of BARDA. In addition to product procurement, the contract includes reimbursed post-marketing activities of about $12 million.

Tembexa News

September 26, 2022 - “The addition of TEMBEXA to our smallpox medical countermeasure franchise, which consists of our smallpox vaccine and therapeutic for smallpox vaccine complications, creates a more comprehensive offering to combat this deadly public health threat,” said Paul Williams, SVP government/MCM business at Emergent. “We look forward to supporting the U.S. government’s smallpox preparedness strategy on a broader scale by executing on this BARDA contract.”

June 24, 2022 - Chimerix announced Public Health Agency of Canada awarded a contract up to a $25.3 million agreement to procure TEMBEXA® (brincidofovir). Execution of this contract will be the responsibility of Chimerix.

June 23, 2022 - Chimerix announced a $9.3 million agreement to procure TEMBEXA with a third party outside of North America.

May 16, 2022 - Chimerix announced a definitive agreement with Emergent BioSolutions Inc. to acquire its exclusive worldwide rights to brincidofovir, including TEMBEXA®.

June 4, 2021 - The U.S. FDA approved Tembexa (brincidofovir) to treat smallpox. 

Tembexa Clinical Trials

A Phase 3 Clinical Study of the Safety and Efficacy of CMX001 for the Prevention of CMV Infection in CMV-seropositive HCT Recipients. This was a randomized, double-blind, placebo-controlled, parallel-group multicenter study of oral brincidofovir (BCV) in approximately 450 cytomegalovirus (CMV)-seropositive subjects who had undergone allogeneic hematopoietic stem cell transplantation (HCT). The study consisted of a screening evaluation and a treatment phase of 10 to 14 weeks. Dosing with the study drug (BCV or placebo) was initiated as soon as individual subjects could ingest tablets after transplant but no later than Day 28 post-transplant and was continued through Week 14. All randomized subjects remained in the study and followed the same scheduled study treatment. Study assessments were performed weekly from randomization through completion of the first post-treatment follow-up assessment at Week 15, and every 3 weeks thereafter through Week 24.

Clinical Trials

No clinical trials found