POSTER HotSpot SITC October 2024 FInal.pdf

Peripheral Blood and Tumor Gene Expression as Biomarkers and Potential Predictors of Clinical Outcome with HST-1011, an Oral CBL-B inhibitor

Introduction

The E3 ligase Casitas B-lineage lymphoma proto-oncogene B (CBL-B) is a master negative regulator of the immune system. CBL-B controls T-cell/NK cell activation and co-stimulatory pathways, including the signaling threshold for T-cell (TCR) activation.

Targeting CBL-B may enable immune activation even in tumors with low antigen levels, low intratumoral inflammation, inadequate co-stimulation and/or active immune suppression associated with poor response/resistance to existing immune checkpoint inhibitors.

As part of the ongoing HST-1011 Ph1/2 (NCT05662397) clinical study, herein we provide preliminary biomarker evaluations in both peripheral samples and tumor tissue.

Methods

RNA isolated from peripheral blood samples at timepoints on Cycle 1 Day 1, Day 8 and Cycle 2 Day 1 were profiled on the Nanostring Immunology V2 chip and used to evaluate changes in T and B-cell receptor (TCR and BCR) repertoires using a 7-chain next generation sequencing (NGS) assay from iRepertoire, Inc.

Paired tumor biopsies were collected from patients and whole exome (WES) and whole transcriptome (WTS) data was generated using the Caris Life Sciences tissue (NGS) assay. Tumor NGS data was used to 1) evaluate expression level of tumor infiltrating lymphocytes (TILs), 2) test different RNA based signatures.

Table 1. Clinical Evaluation and Patient Samples

Overall A1 Population Patients with Clinical Benefit Patients with No Clinical Benefit
Definition Patients who had tumor shrinkage by their first scan; were on treatment beyond first scan Patients with clear progression on HST-1011 at or before the time of their first scan
28 Patients 10 out of 28 patients showed signs of clinical benefit(data presented at ESMO2024) 18 patients with no clinical benefit
Part A1 Tumor NGS Data 4 patients available for analysis: (ovarian, 2 NSCLC, H&N) 9 patients available for analysis

A gene expression signature was derived from a range of in vitro and in vivo models that demonstrated consistent changes in response to CBL-B inhibition. (A) in vivo mouse model showing a dose dependent increase in the response signature in PBMCs (B) Dose-related increases in signature expression were observed from patients treated with HST-1011.

Impact of HST-1011 on Modulation of Different Immune Related Pathways

HST-1011 induced dose dependent modulation of immune related transcriptional pathways in peripheral blood samples.

Impact of HST-1011 on TCR and BCR Repertoire Metrics from Peripheral Samples After 1 Cycle of Treatment

HST-1011 induced changes in different TCR and BCR repertoire metrics: (A) Decrease in TCR diversity index (beta and alpha) D50 in patients who benefitted from HST-1011 therapy suggesting a focused T-cell response. (B) Patients with clinical benefit showed an increase in naive B-cells undergoing mutations, and the class switch ratio (CSR) indicating an adaptive immune response.

Tumor NGS Data from Patients Treated with HST-1011: Screening and On-treatment Biopsies

(A) Tumor NGS shows higher TILs in patients with evidence of clinical benefit following HST-1011 treatment. (B) Modulation of a CBL-B response signature in on-treatment (Day 15) biopsy samples with increased expression of the signature seen in patients benefiting from HST-1011 therapy compared to those with no benefit.

Assessment of a TME RNA Signature on Baseline Tumor Samples (N=13): Biological Complexity Reduced to Two Axes

TME RNA signature testing to predict clinical benefit: Patients with high immunesignature scores tend to benefit HST-1011 treatment; patients with limited or no clinical benefit were identified accordingly.

Conclusions

An HST-1011 derived response signature showed a consistent dose dependent increase in patient peripheral blood.

Patients with clinical benefit showed higher expression of the response signature in their on-treatment tumor biopsies.

Preliminary TCR and BCR repertoire NGS data showed HST-1011 impacted both immune cell populations with changes in several metrics that were associated with clinical benefit.

Patients who benefitted from HST-1011 treatment showed higher TIL expression in their baseline tumor biopsies, and their tumors were in the immune categories when testing a TME RNA signature.

References

  1. Bachmaier K, Krawczyk C, Kozieradzki I, et al. Negative regulation of lymphocyte activation and autoimmunity by the molecular adaptor Cbl-b. Nature. 2000;403(6766)211-216.

  2. Sharma P, Hu-Lieskovan S, Wargo JA, Ribas A Primary, Adaptive, and Acquired Resistance to Cancer Immunotherapy. Cell. 2017;168:70-723.

  3. Chiang YJ, Kole HK, Brown K et al. Cbl-b regulates the CD28 dependence of T-cell activation. Nature. 2000;403(6766:216-220.

  4. Danaher P, Warren S, Dennis L, DAmico L, et al. Gene expression markers of tumor infiltrating leukocytes. J. Immunol. of Cancer. 2017; (5): 18.

  5. Uhlik, et al. AACR 2022.

  6. iRepertoire, Inc., Huntsville, AL.

  7. Caris Life Sciences, Phoenix, AZ.