Preprint Club
A cross-institutional Journal Club Initiative

Keywords

• Cancer immunotherapy

• Regulatory T cells

• CD8+ T cells

Main Findings

Up to now, several types of immunotherapy have been developed and used as single or combination methods to obtain durable clinical responses. However their efficacies are variable and only subsets of cancer patients benefit from them. Especially, on-target, off-tumor toxicity severely limits systemic dosing of cytokines and agonist antibodies for cancer therapy. To mitigate this problem, intratumoral administration is increasingly being explored. In this preprint, the authors report the development of a tumor-anchored α4-1BB agonist (α4-1BB-LAIR) which consists of an α4-1BB antibody fused to the collagen binding protein LAIR1 (Leukocyte Associated Immunoglobulin Like Receptor 1), in combination with TA99. TA99 is an antitumor antibody that binds to Trp1 on the surface of B16F10 melanoma, the poorly immunogenic tumor mouse model used in this study. The authors further explored the role of T cells by the use of αCD4 or αCTLA-4 antibody. Main results:

• TA99 + α4-1BB-LAIR (Tx) synergizes robustly with CD4 compartment depletion, boosted cure rates to over 90%. Mechanism: αCD4 induces de novo priming in the tumor draining lymph node (TdLN), leading CD8+ T cell infiltration to tumor. Tx + αCD4 drives a robust cytotoxic T cell program resulting in the tumor rejection. However, upon re-challenge with tumor cells, mouse failed to be protected, demonstrating the need of CD4 for long term memory generation.

• Elimination of regulatory T cells (Tregs) was sufficient to boost the efficacy of Tx and eliminated the tumor cells. In addition, Tregs depletion, by maintaining the CD4+ effector population allows for the proper formation of long-term immune memory and the rejection of tumor upon re-challenge.

• αCTLA-4 therapy, a clinically approved antibody that enhances T cell priming also synergizes with TA99 + α4-1BB-LAIR, produced equivalent cure rates while additionally generating robust immunological memory against secondary tumor rechallenge with 100% of survivors that rejected second tumor.

Limitation

• The preprint presents data of bulk RNA-sequencing of CD45+ cells in tumor and drain lymph node. These results show that CD4 depletion increased CD8+ T cell program. It would be interesting to investigate isolated CD8+ T cell population to determine whether those differences are merely quantitative or also qualitative.

• It would be interesting to validate the “response signature” observed in the bulk RNA-sequencing by additional methods, such as immunohistochemistry or immunofluorescence.

• The authors used a poorly immunogenic mouse model with B16F10 melanoma challenge, but the results would be strengthen by the use of additional models of tumor.

Significance/Novelty

The data clarify the mechanism how the combination of systemic TA99, intratumoral α4-1BB-LAIR, simultaneously CD4+ T cell depletion by intratumoral αCD4 therapy, achieves a maximum efficacy in poorly immunogenic B16F10 melanoma cells inoculated mouse model (cure rates over 90%). The depletion of Tregs and preservation of CD4+ effector T cells by using intratumoral αCTLA4 (a clinical approved drug) led to a robust long-tern immunological memory with 100% of cured mice rejecting secondary tumor rechallenge. These results provides a strong rationale and promising future for development of Treg-directed therapies in combination with proper immune agonists, to achieve a high treatment efficacy even in immunologically cold tumors.

Credit

Reviewed by Thi My Hanh Luong as part of a cross-institutional journal club between the Icahn School of Medicine at Mount Sinai, the University of Oxford, the Karolinska Institute and the University of Toronto.

The author declares no conflict of interests in relation to their involvement in the review.