Background
For HIV patients, there is currently no effective cure. Approaches involving stem cell and gene therapies aimed at mimicking the results of the Berlin Patient and others have been developed including ongoing human clinical trials. There is an urgent need for strategies that expand gene therapy beyond CCR5 modification to target multiple stages of HIV replication.
Methods
Thus, we completed a Phase I clinical trial, on behalf of the AIDS Malignancy Consortium (grant UM1CA121947), enrolling HIV-related lymphoma patients requiring an autologous transplant. Following BEAM conditioning, participants received autologous peripheral blood CD34+ cells transduced with a lentiviral vector containing three HIV-resistance genes, a CCR5 shRNA, a chimeric TRIM5alpha gene, and a TAR decoy. A fourth gene was included and used as a selectable marker to purify the gene modified cells prior to transplant. Three cohorts of participants (total N=11) each receiving the gene modified cells in a dose dependent ratio along with unmodified cells: 1:1, 2:1, 1:0 were enrolled.
Results
Safety of the vector transduced cells was determined by (1) predetermined engraftment timelines and (2) by average vector copy number in the peripheral blood post-transplant by quantitative PCR. Flow cytometry of immune cell reconstitution in the peripheral blood was also evaluated. In all participants, successful and steady engraftment was observed over the course of one to two years. One participant underwent an optional analytical treatment interruption (ATI) 42 months post-transplant. Criteria for ATI included CD4 >300 and undetectable plasma viral load. Upon analysis of vector copy number in the peripheral blood, an 8-fold increase in gene marking was observed at seven weeks post-ATI. An in-house single-cell droplet PCR method to evaluate HIV infection in this patient’s cells during the ATI estimated that approximately 75% of the gene modified cells were protected from de novo infection compared to cells without detectable lentiviral vector DNA. This protection of infection was similar at both early and late ATI timepoints. ATI was suspended on week 8, after the CD4 and plasma viral load safety thresholds were met. CD4 rose to >300 one week post-treatment resumption and viral load became undetectable by week 8.
Conclusions
Our results highlight both the safety and efficacy of our approach and warrants further assessment.