Presentation on theme: "Findings and Challenges in Product Testing and Patient Monitoring for RCR/L in Gene Therapy Clinical Trials Gwendolyn Binder-Scholl, Ph.D. University of."— Presentation transcript:
1Findings and Challenges in Product Testing and Patient Monitoring for RCR/L in Gene Therapy Clinical TrialsGwendolyn Binder-Scholl, Ph.D.University of PennsylvaniaTranslational Research Program
2Overview Challenges of Biologic RCR/L Testing on Cell Products Summary of Retroviral Gene Therapy Trials in the TRPDetailed Testing Summaries for each TrialDiscussion Points
3Challenges biologic RCR/L testing on cell products TimingIncreases enrollment-infusion time ~4-6 weeks(an alternative rapid method such as PCR may be used to provide an initial analysis when transduced patient cells must be administered immediately. But a culture based RCR/L assay should be initiated for retrospective confirmation).Costcell manufacture ~$15K-$20Kvector costs ~$15-30K per patientbiological RCL testing is ~$22KRiskTheoretical and never observedRisk is theoretical and never observed with manufacturing methods used for clinical trials to date
4RCR/L Testing SummaryNo RCR/L detected: 12 vector and 34 cell lots; 31 patients3 different vector types and production systems: MLV, crHIV, sinHIVUp to 9 years follow-up in vivoINDYear openVector typeTransgeneProduction MethodRCR / RCL VectorRCR / RCL in CellsRCR / RCL in vivoYears follow-up85681999MLVCD4-ζ CIRProducer cells10/30/110/105-9yr127992006cr-HIVHIV env antisenseTransient transfection20/70/200/181-4 yr139602009SIN-HIVCD19-CIRTransient transfection30/2<114122High affinity gag-TCR0/1pendingFor 8568 there were parallel trials Sponsored by Cell Genesys 44 patients up to 10 year follow-upFor there were additional trials sponsored by VIRxSYS as summarized by Dr. Humeau, including the first 5 lv vector treated patients which were treated at Penn and are up to 7 years follow-up1 PA317 cell line unpublished2Lu et al, J. Gene Med., 20043Zufferey et al, Nat. Biotech., 1997
5RCR Testing in IND 8568 (MLV) Clinical indication: HIV; CD4-zeta CIRTarget cells: CD4 and CD8 T cellsVector and Cell product: Supernatant and cells cocultured with M. dunni cells-approximately 1% of total cell product/EOP and 300ml supernatant cocultured with M. dunni cells-+ control ( ffu amphotrophic MLV)-5 passages cell product (~3 weeks); 2 passages sup (~1-1.5 week)- test in feline PG-4 S+L- focus forming assayPatient Monitoring:-PCR amplification of a 70 bp region of the amphotrophic envelope in PBMCs-baseline, ~ quarterly to 1 year, and annually thereafter (protocol later modified to reflect current guidance on monitoring for delayed adverse events)Now am going to talk about specific RCR/RCL testing under specific TRP sponsored INDs
6RCL Testing in IND 12799 (crHIV) Clinical indication: HIV; env antisenseTarget Cells: CD4 T cellsVector product: 5% final vector fill and 1% EOP cells at VIRxSYS Corporation in C cells-attenuated HIV positive control (Schonely et al, Bioprocessing J, 2003)Cell product: (no biologic RCL test)-PCR based assay for VSV-G envelope-PCR based assay monitoring HIV gag pre and post expansionPatient Monitoring:-PCR amplification for VSV-G envelope in PBMCs at a minimum quarterly and then annually (if negative at year 1, then archived for look back)IND cross referenced VIRxSYS IND-presented by Dr. Humeau, for RCL testing.Final fill was tested instead of vector supernatant because crude supernatants were found to be inhibitory to RCL detection-as publishedStrategy for PCR assay was developed in close proprietary consultation with the FDA. Generally because VIRxSYS submitted data showing that testing of the cell product was not sufficiently sensitive to detect an RCL.
7RCL Testing in IND 14122 (SIN-HIV) Clinical indication: HIV; HIV gag CTLsTarget cells: CD8 T cellsVector product: 300ml sup and 1% EOP cells at Indiana University using the C cell line-R8.71 VSV-G pseudotyped attenuated HIV positive controlCell product: (no biologic RCL)-PCR based assay for VSV-G envelopePatient Monitoring:-PCR amplification for VSV-G envelope in PBMCs at a minimum quarterly and then annually (if negative at year 1, then archived for look back)In close consultation with the FDA, we developed a plan for RCL release testing on the cell product that involved only molecular based assays.
8Molecular RCL Testing for Cell Product Release 14122 case study +vector+ARVHigh affinity HIV gag TCR targeting SL9 epitope expressed by a SIN–HIV vectorCD820% CD4HarvestDay:39-12RCL testingVSV-G DNAIn consulation with FDA, determined no biologic RCL necessary:ARV in media, no RCL amplificationCD4 T cells added after vector washoutRetroviruses are not stable at 37°C, losing 90% of titer each 48 hours (Higashikawa and Chang, Virology, 2001). Without amplification, residual RCL from the vector reduced 10,000 fold in 8 day culture. Fewer than 250 IU RCL are added to culture based on the LOD of the vector RCL assay.20% CD4 T cells and 20% v/v conditioned mediaPost gag is not statistically great than pre (unique situation since final product is typically <5% CD4 T cells)CD8 T cells are enriched by elutriation and negative selectionConcentration of ARV is 1ug/ml of AZT and 500 nM ritonavir
9Molecular RCL Testing on Cell Products 14122 case study-PCR sensitivity Testing 1% of cell product not feasible.The # of cells required to have 95% confidence that the sample is negative =10,000 cells / 0.06 µg DNAEstablished test evaluates 450,000 cells / 3 µg DNAAdapt p=1-exp(-cVt) : the probability of not detecting at least 1 RCR(FDA 2006 Supplemental Guidance on RCR testing)We see a 1/2 log reduction in sensitivity of spike recovery if spike is performed pre isolation. May be different if td cell line used. Given the number of cells in the final cell product, we know there are fewer than 6666 copies of VSV-G in the cell culture
10Molecular RCL Testing on Cell Products 14122 case study-PCR sensitivity Vt=-(1/c)ln(1-p)Current Guidance-Vt is the volume-c is the 1 IU/100ml-p is 95% confidenceAdapted for DNA testing-Vt is the ug of DNA (# cells)-c is 50 copies / ug genomic DNA(1:3000 cells)-p is 95% confidenceAssay can detect ≤ 50 VSV-G copies / µg genomic DNA: Vt=-(1/50)ln(1-0.95)-FDA Guidance-Feasible LOD for a PCR assay-Empirically determined through spike and recovery studiesThis approach was discussed with and approved by the FDA. A potential discussion point for the committee may be the biological relevance of this method and it’s usefulness for a broader application across retroviral vector based cell therapies.
11RCL Testing in IND 13960 (SIN-HIV) Clinical indication: CD19+ leukemia and lymphomas; CD19-CARTarget cells: CD4 and CD8 T cellsVector product: 300ml sup and 1% EOP cells at Indiana University using the C cell lineCell product:-p24 in T cell culture-PCR based assay for VSV-G envelope and HIV gag-Coculture of final product (1% or 1e8 cells) with C cells in method used in Escarpe et al, Mol Ther., 2006)-R8.71 positive control ~100 IUPatient Monitoring:-PCR amplification for HIV-gag in PBMCs at a minimum quarterly and then annually (if negative at year 1, then archived for look back)
12Molecular RCL Testing on Cell Products IND 13960 Case Study +vectorCD19-41BB-ζ CAR, expressed by a SIN–HIV vectorCD4/8HarvestDay:39-12RCL testingHIV gag DNAP24VSV-G DNACo-culture with C8166 cellsBiological RCL assay because:Antiretrovirals are not included in the culture media,Spiking studies with R8.71 showed that 100 IU RCL could be carried through to the end of culture-not detectable by end of culture p24-not detectable by amplification of end of culture supernatant with C8166-detectable by co-culture with C8166 cellsThe amount of vector used could theoretically contain >500 IU RCL given a LOD of 5 IU/ml from the vector RCL assayCells expanded post vector wash out in a static system or in a perfusion bioreactor which allows for greater exchange of media to remove residual vector proteins and DNA.
13Molecular RCL Testing on Cell Products IND 13960 Case Study-Residual vector protein/DNA Patient 1Patient 2Patient 3Cell populationdoublingNegativeHIVgag copies/µgMedia exchange is proportional to the amount of cell expansion. Patients 1 and 3 underwent expansion in a perfusion bioreactor, but patient 2 did not. Mention here the residual testing, and cite that the LV vector titer was low and so a large volume (~110 ml) had to be added. Old vector process only used TFF-new process now available that uses anionic exchange followed by TFF and size exclusion chromatography.p24 pg/mlCulture day
14Discussion PointsNot all cell manufacturing processes are equal. When might biologic RCL testing for cell products be informative?:-when using vectors with high levels of residual packaging DNA/protein-addition of high amounts of vector (low titer)Biological RCL testing on cell products is a major burden. Potential solutions are:a. Use molecular approaches for RCR/L testing on cell products-in which cases would this be acceptable?b. Develop a funding initiative to defray the costs associated with amplification based RCR/L testing, or,c. Establish discounted services to perform amplification based RCL testing (such as the NGVL initiative)FDA Guidance for RCR/L annual archive could follow current guidance for monitoring for delayed adverse events. If gene modified cells no longer detected at 5 year, no RCR/L sample collection for archive should be required.In what cases would molecular testing be acceptable?
15AcknowledgementsUniversity of Pennsylvania City of Hope, Center for Biomedicine & GeneticsCarl June Larry CoutureBruce Levine David HsuZoe ZhengCell Genesys NIH, NIAIDKristen Hege Sarah ReadMitch Finer Frosso VoulgaropoulouSandra BridgesVIRxSYS U19 AI066290Gerard McGarrity U19 AI082628Laurent HumeauAlliance for Cancer Gene TherapyLentigenBoro Dropulic