Drugs

SB-728-T

Other Names: CCR5-ZFN, CCR5-specific zinc finger protein nuclease, SB-728, SB-728mR modified T cells, SB-728mR-T Drug Class: Gene Therapy Products Registry Number: S900006290 (ChemID) Organization: Sangamo Therapeutics Phase of Development: SB-728-T is in Phase 1/2 development for HIV treatment.

(Compound details obtained from ChemIDplus Advanced,1 Treatment Action Group website,2 and Viruses article3)

Pharmacology


Mechanism of Action: Gene therapy product (zinc finger nuclease [ZFN]-mediated CCR5 gene modified cells). SB-728-T is a product generated by using ZFNs that are delivered via an adenovirus vector or mRNA to modify autologous CD4 cells at the CCR5 gene. Engineered ZFNs targeting CCR5 are designed to produce a double-stranded break at a specific site in the CCR5 gene coding region. The site is located upstream of the naturally occurring homozygous CCR5-delta-32 mutation, which is known to confer resistance to HIV-1 infection. Upon CCR5 DNA cleavage by ZFNs, innate error-prone DNA repair mechanisms are induced, leading to permanent disruption of CCR5 expression on CD4 cells.3-7 SB-728-T gene therapy may provide individuals who have HIV with a reproducible pool of CD4 cells permanently resistant to HIV entry, potentially improving immune restoration and leading to functional control of HIV.8,9

An SB-728-T cell product containing a mixture of CCR5-modified autologous CD4 cells and CD8 cells is also being studied. The mixed CD4/CD8 SB-728-T product allows for a simpler manufacturing process and potentially greater antiviral effect.10,11

Half-life (T½): In a study (NCT00842634) of 12 participants with HIV who received a single dose of SB-728-T, modified CD4 cells had an estimated mean half-life of 48 weeks.12


Select Clinical Trials


SB-728-T: Autologous CCR5-Modified T Cell Product Generated via Adenoviral Delivery of ZFNs
Study Identifiers: SB-728-1101; NCT01543152
Sponsor: Sangamo Therapeutics
Phase: 1/2
Status: This study has been completed.
Study Purpose: The purpose of this open-label dose escalation study was to evaluate the safety and efficacy of cyclophosphamide preconditioning when used to enhance SB-728-T engraftment.
Study Population: Participants were adults with HIV who had been on ART for at least 6 months and had undetectable viral load levels for 3 months prior to study entry. At study entry, participants were on a stable ART regimen, had undetectable viral load levels, and had CD4 counts ≥500 cells/mm3.10,13

Selected Study Results:

Study Identifiers: TRAILBLAZER; NCT03666871
Sponsor: Case Western Reserve University
Phase: 1/2
Status: This study is currently recruiting participants.
Study Purpose: The purpose of this study is to compare the effect of SB-728-T versus ex vivo expanded unmodified autologous CD4 cells on the size of the latent HIV reservoir in participants with HIV.
Study Population: Participants are adults with HIV who are on a stable ART regimen. Participants have had HIV RNA <50 copies/mL for at least 48 weeks and have CD4 counts >350 cells/mm3 at screening.14

SB-728mR-T: Autologous CCR5-Modified T Cell Product Generated via mRNA Delivery of ZFNs
Study Identifiers: SB-728mR-1401; NCT02225665
Sponsor: Sangamo Therapeutics
Phase: 1/2
Status: This study has been completed.
Study Purpose: The purpose of this open-label study was to evaluate the safety and effectiveness of repeat doses of SB-728mR-T following cyclophosphamide preconditioning in individuals with HIV.
Study Population: Participants were adults with HIV who were on ART and who had initiated ART ≤1 year of HIV diagnosis or suspected infection. Participants had undetectable viral loads for at least 2 months prior to and at screening and had CD4 counts ≥500 cells/mm3 at study entry.15

Selected Study Results:

Other studies evaluating SB-728-T gene therapy have been completed or are planned. These include the following Phase 1 studies:
  • SB-728-0902 (NCT01044654): This is a completed study that evaluated the safety and effectiveness of SB-728-T in individuals with HIV who had suboptimal CD4 counts while on ART.8
  • SB-728mR (NCT02388594): This is a completed trial that investigated a single infusion of SB-728mR, with and without cyclophosphamide preconditioning, in participants with HIV who were receiving ART.16
  • NCT03617198: This is a pilot study that is examining whether treatment with autologous T cells modified by SB-728mR and CD4 chimeric antigen receptor is safe and effective in adults with HIV. This study is currently recruiting participants.17
  • SB-728-1003 (NCT04201782): This is a long-term follow-up study of participants who have received SB-728-T or SB-728mR-T in a previous trial and completed 3 years of post-infusion follow-up. This study does not involve any treatment. This study has been enrolling by invitation.18


Adverse Events


SB-728-1101 (NCT01543152):

In this Phase 1/2 study, participants were enrolled into five cohorts, with each cohort receiving a different dose of cyclophosphamide prior to SB-728-T infusion. Mild infusion reactions, including low-grade fever and chills, were associated with SB-728-T. A garlic-like odor (due to dimethyl sulfoxide) was also reported with SB-728-T infusions.13,19

Cyclophosphamide was reported as being safe at doses up to 1 g/m2. In Cohort 2 (cyclophosphamide 500 mg/m2), two out of three initial participants experienced Grade 2 nausea and vomiting. Three participants subsequently enrolled into Cohort 2 received prophylactic antiemetics. In Cohort 4 (cyclophosphamide 2 g/m2), one participant had Grade 4 neutropenia, and two participants had Grade 3 neutropenia. Two of the three participants in Cohort 5 (cyclophosphamide 1.5 g/m2) developed Grade 4 neutropenia.19,20


Drug Interactions


Drug-drug interactions associated with SB-728-T are currently unknown.


References


  1. United States National Library of Medicine. ChemIDplus Advanced: SB-728-T https://chem.nlm.nih.gov/chemidplus/sid/s900006290. Accessed July 22, 2020
  2. Treatment Action Group website. Research toward a cure trials. http://www.treatmentactiongroup.org/cure/trials. Accessed July 22, 2020
  3. Manjunath N, Yi G, Dang Y, Shankar P. Newer gene editing technologies toward HIV gene therapy. Viruses. 2013;5(11):2748-2766.
  4. Blick G, Lalezari J, Hsu R, et al. Cyclophosphamide enhances SB-728-T engraftment to levels associated with HIV-RNA control. Abstract presented at: Conference on Retroviruses and Opportunistic Infections (CROI); March 3-6, 2014; Boston, MA. Abstract 141. http://www.croiconference.org/sessions/cyclophosphamide-enhances-sb-728-t-engraftment-levels-associated-hiv-rna-control. Accessed July 22, 2020
  5. Perez EE, Wang J, Miller JC, et al. Establishment of HIV-1 resistance in CD4+ T cells by genome editing using zinc-finger nucleases. Nat Biotechnol. 2008;26(7):808-816.
  6. Maier DA, Brennan AL, Jiang S, et al. Efficient clinical scale gene modification via zinc finger nuclease–targeted disruption of the HIV co-receptor CCR5. Hum Gene Ther. 2013;24(3):245-258. Sangamo Therapeutics: Press Release, dated October 16, 2014.
  7. Sangamo BioSciences ZFP therapeutic program in HIV/AIDS featured at three major scientific conferences in October 2014. https://www.prnewswire.com/news-releases/sangamo-biosciences-zfp-therapeutic-program-in-hivaids-featured-at-three-major-scientific-conferences-in-october-2014-279399672.html. Accessed July 22, 2020
  8. Sangamo Therapeutics. A Phase 1 dose escalation, single dose study of autologous T-cells genetically modified at the CCR5 gene by zinc finger nucleases SB-278 in HIV-infected patients who have exhibited suboptimal CD4+ T-cell gains during long-term antiretroviral therapy. In: ClinicalTrials.gov. Bethesda (MD): National Library of Medicine (US). Registered on January 6, 2010. NLM Identifier: NCT01044654. https://clinicaltrials.gov/ct2/show/NCT01044654. Accessed July 22, 2020
  9. Ando D. Functional control of viremia in CCR5-Δ32 heterozygous (Δ32HZ) HIV+ subjects following adoptive transfer of zinc finger nuclease CCR5 modified autologous CD4 T-cells (SB-728-T). Annual Meeting of the European Society of Gene and Cell Therapy (ESGCT and SETGyC Collaborative Congress); October 25-28, 2013; Madrid, Spain. National AIDS Treatment Advocacy Project (NATAP): HIV Articles. http://www.natap.org/2013/HIV/103013_01.htm. Accessed July 22, 2020
  10. Sangamo Therapeutics: Press Release, dated February 26, 2015. Sangamo BioSciences presents new clinical data at CROI 2015 from trial of ZFP Therapeutic® designed to provide functional control of HIV. https://investor.sangamo.com/news-releases/news-release-details/sangamo-biosciences-presents-new-clinical-data-croi-2015-trial. Accessed July 22, 2020
  11. Sangamo Therapeutics: News Release, dated December 11, 2015. Sangamo BioSciences presents Phase 2 clinical data from two SB-728-T HIV studies. https://investor.sangamo.com/news-releases/news-release-details/sangamo-biosciences-presents-phase-2-clinical-data-two-sb-728-t. Accessed July 22, 2020
  12. Tebas P, Stein D, Tang WW, et al. Gene editing of CCR5 in autologous CD4 T cells of persons infected with HIV. N Engl J Med. 2014;370(10):901-910.
  13. Sangamo Therapeutics. A Phase I, open-label study to assess the effect of escalating doses of cyclophosphamide on the engraftment of SB-728-T in viremic HIV-infected subjects on HAART. In: ClinicalTrials.gov. Bethesda (MD): National Library of Medicine (US). Registered on March 1, 2012. NLM Identifier: NCT01543152. https://clinicaltrials.gov/ct2/show/NCT01543152. Accessed July 22, 2020
  14. Case Western Reserve University. T-cell reinfusion after interfering with lymphocyte binding location of AIDS virus through zinc-finger-nuclease elimination of CCR5 receptors: The TRAILBLAZER Study. In: ClinicalTrials.gov. Bethesda (MD): National Library of Medicine (US). Registered on September 7, 2018. NLM Identifier: NCT03666871. https://clinicaltrials.gov/ct2/show/NCT03666871. Accessed July 22, 2020
  15. Sangamo Therapeutics. A Phase 1/2, open-label study to assess the safety and tolerability of repeat doses of autologous T-cells genetically modified at the CCR5 gene by zinc ginger nucleases in HIV-infected subjects following cyclophosphamide conditioning. In: ClinicalTrials.gov. Bethesda (MD): National Library of Medicine (US). Registered on August 22, 2014. NLM Identifier: NCT02225665. https://clinicaltrials.gov/ct2/show/NCT02225665. Accessed July 22, 2020
  16. University of Pennsylvania. A Phase I study of T-cells genetically modified at the CCR5 gene by zinc finger nucleases SB-728mR in HIV-infected patients, with or without the CCR5 delta-32 mutation, pre-treated with cyclophosphamide. In: ClinicalTrials.gov. Bethesda (MD): National Library of Medicine (US). Registered on February 24, 2015. NLM Identifier: NCT02388594. https://clinicaltrials.gov/ct2/show/NCT02388594. Accessed July 22, 2020
  17. University of Pennsylvania. A pilot study of T cells genetically modified by zinc finger nucleases SB-728mR, C34-peptide conjugated to the CXCR4 N-terminus, and CD4 chimeric antigen receptor in HIV-infected subjects. In: ClinicalTrials.gov. Bethesda (MD): National Library of Medicine (US). Registered on July 9, 2018. NLM Identifier: NCT03617198. https://clinicaltrials.gov/ct2/show/NCT03617198. Accessed July 22, 2020
  18. Sangamo Therapeutics. Long-term follow-up of HIV-infected subjects treated with autologous T-cells genetically modified at the CCR5 gene by zinc finger nucleases (SB-728-T or SB-728mR-T). In: ClinicalTrials.gov. Bethesda (MD): National Library of Medicine (US). Registered on December 13, 2019. NLM Identifier: NCT04201782. https://clinicaltrials.gov/ct2/show/record/NCT04201782. Accessed July 22, 2020
  19. Blick G, Lalezari J, Hsu R, et al. A dose escalation study of cyclophosphamide (CTX) to enhance SB-728-T engraftment. Conference on Retroviruses and Opportunistic Infections; February 23-26, 2015; Seattle, WA. Levin: Conference Reports for National AIDS Treatment Advocacy Project (NATAP); 2015. http://www.natap.org/2015/CROI/croi_81.htm. Accessed July 22, 2020
  20. Ando D, Lalezari J, Blick G, et al. HIV protected autologous zinc finger nuclease CCR5 modified CD4 cells (SB-728-T) reduce viral load (VL) in HIV subjects during treatment interruption (TI): correlates of effect, and effect of cytoxan conditioning. Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC); September 5-9, 2014; Washington, DC. Mascolini: Virologic Response During ART Interruption After CCR5-Cell Modification With SB-728-T (zinc fingers); Conference reports for National AIDS Treatment Advocacy Project (NATAP); 2014. http://www.natap.org/2014/ICAAC/ICAAC_36.htm. Accessed July 22, 2020


Last Reviewed: July 22, 2020