Autologous Stem Cell Transplantation (ASCT) for AIDS-Related Lymphomas (ARL) and the Potential Role of HIV-Resistant Stem Cells.

Background: Optimal therapy of ARL relies on both effective anti-tumor chemotherapy and successful control of the underlying HIV infection. Management of HIV using HAART has been hampered by patient non-compliance with complex regimens, drug resistance and ongoing low level viral replication. Multiplexed RNA based anti-HIV gene transfer strategies to confer intrinsic cellular resistance may help circumvent these problems. Autologous stem cell transplantation for ARL is an ideal clinical platform for delivery of SiRNA transduced stem cells as combining gene transfer strategy with high dose antilymphoma therapy could provide control of both the HIV infection and the ARL.

Methods: Gene transfer - anti-HIV RNA elements, including short hairpin RNA (shRNA) targeted to HIV tat/rev, a TAR-specific decoy sequence, and a ribozyme targeted to CCR5 were combined into a lentivirus vector (LV, rHIV7-shI-TAR-CCR5RZ). Using LV transduction methods, these anti-HIV RNAs were delivered into CD34+ hematopoietic progenitor cells (HPC).

Results: Preclinical vector development - LV transduction allowed differentiation in liquid culture and in a SCID-hu model which produced macrophage and T cell progeny that were resistant to the HIV virus. Although HIV resistance can be induced in vitro with single anti-HIV shRNAs, no resistance was found in multiply passaged HIV in rHIV7-shI-TAR-CCR5RZ-transduced cells. In addition, cells were analyzed by microarray for mRNA and miRNA alterations and no significant changes were noted between CD34 transduced and untransduced cells. Copy number in transduced cells was 1–2/cell, and integration site analysis localized to transcriptionally active sites, usually away from terminal portions of gene sequences. This vector is proposed for use in ASCT for ARL.

Update of ASCT in ARL: Between 1998 and 2006, 28 patients with high-risk ARL underwent ASCT at the City of Hope. Conditioning regimens included CBV (cyclophosphamide (Cy)100mg/kg, Carmustine150 mg/m2, VP16 60mg/kg) in 24 and FTBI/Cy/VP16 in 4. All patients engrafted, median time to ANC>500 was 11 days (range, 8–19). Regimen related toxicities included grade 3–4 hepatic toxicity n=3 and interstitial pneumonitis n=2. OI’s included PCP pneumonia n=2, CMV infection (2 viremias, 1 retinitis) and 2 cases of VZV. Therapy-related MDS was seen in one patient who ultimately died of MDS while in remission from his ARL. Median HIV viral load (VL) at ASCT was 6113 gc/ml with 22 having an undetectable VL. At two years only 9 pts had an undetectable VL. Median CD4 count at ASCT was 164 (range 25–1064), this rose to 263 (95–1164) at two years post ASCT. With a median f/u of 41 months, 2yr OS is 78% (95% CI 63–87) and PFS 78% (95% CI 63–87).

Conclusions: ASCT can lead to durable remission for ARL. The fluctuation in VL seen post ASCT reflects the natural history of HIV infection and limitations of current antiviral therapy. Ultimately the system of gene transfer outlined above combined with ASCT as part of our next generation clinical trial could provide the optimal chance of cure for pts with high-risk ARL by offering both effective antilymphoma and anti-HIV therapy.