Abstract Results

Methods

Conclusions

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T cells capable of targeting neoepitopes (neoE) from tumor-specific mutations hold the potential to recognize and

kill tumor cells. However, most cancer patients fail to mount a sufficient intrinsic T cell immune response to translate into

clinical benefit. PACT Pharma has developed an ultra-sensitive and high-throughput technology (imPACTTM) for identifying and

capture of neoE-specific T cells from blood. Whole exome sequencing of tumors and computational prediction identify

patient-specific neoepitopes from tumor mutations. We then interrogate patient blood for neoE-specific T cells using human

leukocyte antigen (HLA) protein-based reagents comprising a spectrum of HLAs, thus enabling the evaluation of >99% of

cancer patients. We have identified and isolated neoE-specific T cells from the peripheral blood of ~80% treatment-naive

patients with five different solid tumors. Primary human T cells engineered with T cell receptor sequences (neoTCRs)

identified by imPACT gain the ability to kill cognate neoE-presenting tumor cells, confirming the specificity of the isolated

neoTCR to its neoE target. This approach is also amenable to the longitudinal analysis of patients undergoing treatment for

their cancers, to characterize the neoE-specific T cell populations likely to confer clinical benefit. In summary, the imPACT

technology efficiently discovers meaningful intrinsic neoTCRs from patients, enabling the development of personalized

neoTCR-T cell therapies for the eradication of solid tumors.

➢ imPACT technology is efficient for capturing neoE-specific T cells directly from blood of patients with solid tumors

• Useful for all ethnicities - PACT HLA catalog enables imPACT analysis of >99% of all individuals

• imPACT process is ultra-sensitive - capturing neoE-specific T cells at a frequency as low as 1 per 5M PBMC

• imPACT process has been qualified to be robust and reproducible - neoTCRs have been captured from blood of~80% treatment-naive patient with different solid tumors, to date.

➢ imPACT technology is a highly effective platform for immune monitoring of specimens from clinical trials &authenticating tumor-exclusive mutation targets for manufacturing personalized neoTCR-T cell therapies

Figure 3. The theoretical and actual probability of capturing at least one target antigen-specific T cell from blood.

Figure 2. Confirming reproducibility of antigen-specific T cell capture from blood using imPACT technology.

Figure 1. PACT HLA catalog : coverage for >99%of all patients with cancer based from TCGA data (N = 9165).

Figure 6. Robustness of imPACT technology. Number of unique neoTCR clonotypesisolated from blood of patients with melanoma or colorectal, bladder, ovarian, head &neck cancers. NeoTCRs were successfully captured from blood of 12/16 treatment-naïve patients, & 6/7 for patients on anti-PD1 treatment (baseline sample). See Poster4058 for PACT immune monitoring of longitudinal specimens from clinical trials.

Figure 4. imPACT capture of neoE-specific T cells from blood, even from treatment-naïve patients (PACT077, melanoma). (Top) neoE-specific T cells captured in ~5mLblood. Star indicates the same neoTCR clonotype was in TILs. (Middle) clonality &predicted neoE-HLA binding affinity. Green dot: clonal mutation; red dot: sub-clonalmutation. (Bottom) Phenotype characterization of neoE-specific T cells. CD95+ T cellsare antigen-experienced.

Figure 5. Validation of imPACT-captured neoE-specific T cell specificities. Percentageof neoTCR gene-edited lymphocytes that recognize the PACT077 cognate antigens. SeePoster 4858 for PACT precision genome engineering technology; see Poster 3758 forPACT neoTCR functional characterization.

Gene HLA neoE (wild type AA) TCR No.

SLC38A1 B18:01 DEYIPGTTF(S) TCR164CDKL2 A24:02 IYNII(N)VTTL TCR135

SLC38A1 A24:02 EYIPGTTF(S)L TCR142, 145, 139 & 136MADD A02:01 HLS(P)LELLGVD TCR143PARK2 A02:01 K(E)TSVALHLI TCR144

CD

45

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CD95