Mechanism of Action: Nucleoside reverse transcriptase inhibitor. Censavudine (4′-Ed4T), a thymidine analog, is phosphorylated by host cellular kinases to its active triphosphate metabolite (4′-Ed4T triphosphate or 4′-Ed4TTP), with an intracellular half-life of approximately 8.0 to 9.7 hours.4 4′-Ed4TTP inhibits the activity of HIV-1 reverse transcriptase by competing with natural substrates and causing DNA chain termination after incorporating itself into viral DNA.5,6 In vitro, censavudine exhibits more potent activity against HIV-2 than against HIV-1.7,8
Half-life (T½): The apparent half-life of censavudine ranged from 2.3 to 3.7 hours in a single oral-dose escalation study of censavudine in healthy participants in the fed state (10 to 900 mg) and fasting state (100 and 300 mg).9
Metabolism/Elimination: Approximately 60% to 95% of an oral censavudine dose was excreted unchanged in urine in a single oral-dose escalation study of healthy participants in the fed state (10 to 900 mg) and fasting state (100 and 300 mg).9
Resistance: In vitro experiments have shown that virus containing the K65R, Q151M (without M184), and possibly L74V mutations demonstrate hypersusceptibility to censavudine. Meanwhile, thymidine analogue mutation pattern 1 (TAM1) pathway virus has reduced susceptibility, exhibiting increasing fold changes with increasing numbers of mutations. Decreased susceptibility was also associated with virus containing the T69 insertion complex and with a Q151M virus that also contained M184V. Compared to wild-type (wt) virus, TAM2 pathway virus exhibited a 6- to 8-fold reduced susceptibility to censavudine, regardless of the number of thymidine analogue mutations (TAMs). The M184V single substitution has been selected by censavudine in vitro and was shown to induce a 2.3-fold decrease in susceptibility to censavudine.10,11
Censavudine has demonstrated potent in vitro activity against HIV-2, including HIV-2 mutants containing the K65R and Q151M reverse transcriptase substitutions. The M184V mutation in HIV-2 resulted in a 15-fold resistance to censavudine relative to the wild-type HIV-2 strain.7
In a Phase IIa dose-escalation study (EudraCT number 2008-004810-29) of 100 to 600 mg of censavudine monotherapy in treatment-experienced adults, no NRTI-associated resistance mutations were selected after 10 days of monotherapy.11-13 Three participants had a decreased response to censavudine on Day 11, but did not have NRTI-associated mutations at baseline or on Day 11. Three other participants who had TAMs responded well to censavudine treatment.13
A Phase IIb study (NCT01489046) evaluated 100 to 400 mg of censavudine versus tenofovir DF, each administered with efavirenz and lamivudine in treatment-naive adults. Week 48 analysis showed that a higher percentage of participants developed treatment-emergent NNRTI and NRTI mutations in the censavudine groups (regardless of dose) than in the tenofovir DF group.14,15
Study Identifier: EudraCT Number 2008-004810-29
Funding Organizations: Oncolys Pharma and Bristol-Myers Squibb
Study Purpose: The purpose of this dose-escalation study was to evaluate the antiviral activity, safety, and pharmacokinetics of censavudine over 10 days.
Study Population: Participants were HIV-infected, treatment-experienced adults who were off ART for at least 3 months before screening. Participants had HIV RNA ≥5,000 copies/mL and CD4 counts ≥250 cells/mm3.
Dosing: Censavudine was administered as monotherapy. Four groups of participants were sequentially assigned to receive either censavudine (100, 200, 300, or 600 mg) or placebo once daily.12,13,16
Selected Study Results:
: AI467003; NCT01489046
: Bristol-Myers Squibb
: The purpose of this dose-response study was to identify a safe and effective dose of censavudine when combined with efavirenz and lamivudine.
: Participants were HIV-infected, treatment-naive adults and had HIV RNA >5,000 copies/mL and CD4 counts >200 cells/mm3
: Censavudine was administered orally and once daily. Participants were randomized to one of the following 4 groups:
Selected Study Results
- Censavudine 100 mg + censavudine matching placebo + efavirenz + lamivudine
- Censavudine 200 mg + censavudine matching placebo + efavirenz + lamivudine
- Censavudine 400 mg + efavirenz + lamivudine
- Tenofovir DF 300 mg + efavirenz + lamivudine.14,15,17,18
In a 10-day dose-escalation study (EudraCT number 2008-004810-29) of censavudine monotherapy, 22 out of 24 censavudine-treated participants experienced adverse events (AEs), which were mostly mild and unrelated or unlikely related to the study drug. AEs did not appear to be dose related. There were no study discontinuations due to an AE and no Grade 4 AEs. When compared to participants receiving placebo, a greater proportion of participants receiving censavudine reported Grade 2 and 3 AEs. Two censavudine-unrelated serious adverse events (SAEs) occurred in the 600-mg dose group. The most common AEs in the censavudine groups (occurring in more than 10% of participants) were abdominal pain, lymphadenopathy, nausea, headache, and fatigue.13
In the Phase IIb study (NCT01489046) of censavudine versus tenofovir DF through 48 weeks, 2 censavudine-related SAEs (atypical drug eruption; thrombocytopenia) and 2 tenofovir DF-related SAEs (drug induced liver injury; depression and lipodystrophy) led to study discontinuation. One non-study drug-related death occurred. No Grade 2 to 4 AE trends were identified. Grade 2 to 4 laboratory abnormalities were transient and most did not result in study discontinuation.14 In a separate evaluation of bone and metabolic safety data through 48 weeks, bone mineral density (BMD) decline was found to be smaller in the censavudine groups than in the tenofovir DF group. The proportion of participants with greater than 10% or 20% loss of limb fat from baseline was small and was similar between censavudine and tenofovir DF. There was a trend towards accumulation of central and peripheral fat across the censavudine groups, with the highest accumulation in the 400-mg dose group. No meaningful changes in mitochondrial DNA (mtDNA) copy number were seen in any treatment group. When compared with participants in the tenofovir DF arm, participants in the censavudine arms showed a trend for a greater increase in total cholesterol. The increases in total cholesterol in the censavudine arms were not dose-related.18
Censavudine drug interactions are currently unknown.
- United States National Library of Medicine. ChemIDplus Advanced. Available at: http://chem.sis.nlm.nih.gov/chemidplus/rn/634907-30-5. Last accessed on November 22, 2016.
- National Institute of Allergy and Infectious Diseases (NIAID). NIAID ChemDB, HIV Drugs in Development. Available at: http://chemdb.niaid.nih.gov/DrugDevelopmentHIV.aspx. Last accessed on November 22, 2016.
- Oncolys BioPharma website. OBP-601 (Censavudine). Available at: http://www.oncolys.com/en/pipeline/obp-601.html. Last accessed on November 22, 2016.
- Wang X, Tanaka H, Baba M, Cheng YC. Retention of Metabolites of 2',3'-Didehydro-3'-Deoxy-4'-Ethynylthymidine, a Novel Anti-Human Immunodeficiency Virus Type 1 Thymidine Analog, in Cells. Antimicrob Agents Chemother. 2009 Aug; 53(8):3317-24. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2715651/. Last accessed on November 22, 2016.
- Yang G, Wang J, Cheng Y, et al. Mechanism of Inhibition of Human Immunodeficiency Virus Type 1 Reverse Transcriptase by a Stavudine Analogue, 4'-Ethynyl Stavudine Triphosphate. Antimicrob Agents Chemother. 2008 Jun;52(6):2035-42. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2415781/. Last accessed on November 22, 2016.
- Paintsil E, Dutschman GE, Hu R, et al. Intracellular Metabolism and Persistence of the Anti-Human Immunodeficiency Virus Activity of 2',3'-Didehydro-3'-Deoxy-4'-Ethynylthymidine, a Novel Thymidine Analog. Antimicrob Agents Chemother. 2007 Nov;51(11):3870-9. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2151449/. Last accessed on November 22, 2016.
- Smith RA, Raugi DN, Wu VH, et al. The Nucleoside Analog BMS-986001 Shows Greater In Vitro Activity against HIV-2 than against HIV-1. Antimicrob Agents Chemother. 2015 Dec;59(12):7437-46. Available at: http://www.ncbi.nlm.nih.gov/pubmed/26392486. Last accessed on November 22, 2016.
- Smith RA, Raugi DN, Parker K, et al. BMS-986001: A Promising Candidate for HIV-2 Treatment. Abstract presented at: 24th International HIV Drug Resistance Workshop; February 21-22, 2015; Seattle, WA. Abstract 61. Available at: https://www.informedhorizons.com/resistance2015/pdf/RW2015_Book.pdf. Last accessed on November 22, 2016.
- Paintsil E, Matsuda T, Ross J, Schofield J, Cheng YC, Urata Y. A Single-dose Escalation Study to Evaluate the Safety, Tolerability, and Pharmacokinetics of OBP-601, a Novel NRTI, in Healthy Subjects. 16th Conference on Retroviruses and Opportunistic Infections (CROI); February 8-11, 2009; Montreal, Canada. Levin: Conference Reports for National AIDS Treatment Advocacy Project (NATAP); 2009. Available at: http://www.natap.org/2009/CROI/croi_85.htm. Last accessed on November 22, 2016.
- Li Z, Terry B, Olds W, et al. The in vitro cross-resistance profile of the NRTI BMS-986001 against known NRTI resistance mutations. Abstract presented at: International Workshop on HIV & Hepatitis Virus Drug Resistance and Curative Strategies; June 5-9, 2012; Sitges, Spain. Abstract 2. Available at: http://www.intmedpress.com/serveFile.cfm?sUID=8ed08ff3-8b0b-4cda-b481-30a670282653. Last accessed on November 22, 2016.
- Li Z, Terry B, Olds W, et al. In Vitro Cross-Resistance Profile of Nucleoside Reverse Transcriptase Inhibitor (NRTI) BMS-986001 against Known NRTI Resistance Mutations. Antimicrob Agents Chemother. 2013 Nov;57(11):5500-8. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3811251/. Last accessed on November 22, 2016.
- Hwang C, Zhu L, Chan H, et al. Antiviral activity, exposure-response, and resistance analyses of monotherapy with the novel HIV NRTI BMS-986001 in ART-experienced subjects. Abstract presented at: 13th International Workshop on Clinical Pharmacology of HIV Therapy; March 16-18, 2012; Barcelona, Spain. Abstract O_06. Available at: http://regist2.virology-education.com/abstractbook/2012_3.pdf. Last accessed on November 22, 2016.
- Cotte L, Dellamonica P, Raffi F, et al. Randomized Placebo-Controlled Study of the Safety, Tolerability, Antiviral Activity, and Pharmacokinetics of 10-day Monotherapy with BMS-986001, a Novel HIV NRTI, in Treatment-Experienced HIV-1-Infected Subjects. J Acquir Immune Defic Syndr. 2013 Jul 1;63(3):346-54. Available at: http://www.natap.org/2013/HIV/Randomized_Placebo_Controlled_Study_of_the_Safety,.13.pdf. Last accessed on November 22, 2016.
- Gupta SK, Lombaard J, Echevarria J, et al. HIV NRTI BMS-986001 in Antiretroviral-Naïve Subjects: Week 24/48 Analyses. 54th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC); September 5-9, 2014; Washington, DC. Levin: Conference reports for National AIDS Treatment Advocacy Project (NATAP); 2014. Available at: http://www.natap.org/2014/ICAAC/ICAAC_28.htm. Last accessed on November 22, 2016.
Bristol-Myers Squibb. A Phase IIb Randomized, Controlled, Partially Blinded Clinical Trial to Investigate Safety, Efficacy and Dose-response of BMS-986001 in Treatment-naive HIV-1-infected Subjects, Followed by an Open-label Period on the Recommended Dose. In: ClinicalTrials.gov. Bethesda (MD): National Library of Medicine (US). Registered on December 7, 2011. NLM Identifier: NCT01489046. Available at: http://www.clinicaltrials.gov/ct2/show/NCT01489046. Last accessed on November 22, 2016.
- Cotte L, Dellamonica P, Raffi F, et al. A Phase-Ib/IIa Dose-Escalation Study of OBP-601 (4’-ethynyl-d4T, Festinavir) in Treatment-Experienced, HIV-1-Infected Patients. Abstract presented at: 50th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC); September 12-15, 2010; Boston, MA. Abstract H-933. Available at: http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=d89fb4da-4268-4d6b-88ee-4f4ebcd548de&cKey=74572456-29b9-410f-8a57-972c2b0676c3&mKey=%7b93AEED6A-54D4-4EF6-99BD-A9B3CE9FACD9%7d. Last accessed on November 22, 2016.
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Last Reviewed: November 22, 2016