568 Tumor-derived GDF-15 prevents therapy success of checkpoint inhibitors by blocking T-lymphocyte recruitment
2021-11-01

<h3>Background</h3> Immune checkpoint blockade (ICB) can achieve durable responses in a subgroup of patients with metastatic cancer, only. Poor immune effector cell infiltration into the tumor microenvironment is a major obstacle to successful therapy. Growth and differentiation factor 15 (GDF-15) is a divergent member of the TGF-β superfamily and has been linked to feto-maternal tolerance, anorexia but recently also to potent local immunosuppression under physiologic and pathophysiologic conditions. GDF-15 is overexpressed in a wide variety of tumors and may be key factor produced by tumors to prevent effective immune cell infiltration into the tumor and to potently block checkpoint inhibitor activity. <h3>Methods</h3> Effects of recombinant GDF-15 and a proprietary GDF-15 neutralizing antibody (CTL-002) on immune cell trafficking and activation were analyzed by adhesion and interaction assays and in melanoma-bearing humanized mouse models. The impact of GDF-15 overexpression was tested in subcutaneously implanted, GDF-15-transgenic MC38 cells. Additionally, patient GDF-15 serum levels were correlated with immune infiltration and OS in cutaneous melanoma. Associations between GDF-15 serum levels, response to PD-1-based ICB and corresponding OS were assessed in two independent cohorts of melanoma patients. <h3>Results</h3> GDF-15 impairs adhesion of T and NK cells on activated endothelia. In HV18-MK bearing humanized mice, inhibition of GDF-15 strongly enhances infiltration of activated myeloid and lymphoid cells. In MC38 tumors, GDF-15 overexpression can abrogate tumor rejection upon anti-PD-1 therapy. 50% of the mice with GDF-15 overexpressing tumors were, however, rescued when anti-PD-1 was combined with anti-GDF-15 (CTL-002). Likewise, anti-GDF-15 improved responses to anti-CD40 + poly(I:C) in the same tumor model. Clinically, inverse correlations of GDF-15 levels with CD8+ T cell infiltration were shown for melanoma brain metastases. In two independent melanoma patient cohorts, low baseline serum GDF-15 levels predicted clinical response to anti-PD1 treatment and superior OS. Bivariate analysis including LDH indicates that GDF-15 is an independently predictor for poor survival in anti-PD-1 treated melanoma patients. <h3>Conclusions</h3> Tumor-derived GDF-15 blocks the infiltration of immune effector cells into tumor tissues. Neutralizing GDF-15 with CTL-002 restores the ability of immune cells to extravasate blood vessels and enter the tumor microenvironment in vivo. GDF-15 thus represents a promising target for cancer immunotherapy. Antibodies against GDF-15 may support treatments with anti-PD-1 and other immunotherapeutic agents. A clinical trial combining anti-GDF-15 (CTL002) with anti-PD-1 (NCT04725474, submitted Abstract ID 15073) is ongoing. <h3>Ethics Approval</h3> Use of patient samples for this study had been approved by the institutional ethics committee Tübingen (ethic vote 125/2015BO2). Use of surplus sera collected in the University of Zurich Hospital (USZ) Biobank during routine blood draws from consenting metastatic melanoma patients was performed according to IRB approval (KEK.Zh- 647/800) and followed the Declaration of Helsinki on Human Rights. <h3>Consent</h3> All patients had given written informed consent to have clinical data recorded by the Central Malignant Melanoma Registry (CMMR) database.