LFA-1 activation enriches tumor-specific T cells in a cold tumor model and synergizes with CTLA-4 blockade

The inability of CD8⁺ effector T cells (Teffs) to reach tumor cells is an important aspect of tumor resistance to cancer immunotherapy. The recruitment of these cells to the tumor microenvironment (TME) is regulated by integrins, a family of adhesion molecules that are expressed on T cells. Here, we show that 7HP349, a small-molecule activator of lymphocyte function–associated antigen-1 (LFA-1) and very late activation antigen-4 (VLA-4) integrin cell-adhesion receptors, facilitated the preferential localization of tumor-specific T cells to the tumor and improved antitumor response. 7HP349 monotherapy had modest effects on anti–programmed death 1–resistant (anti–PD-1–resistant) tumors, whereas combinatorial treatment with anti–cytotoxic T lymphocyte–associated protein 4 (anti–CTLA-4) increased CD8⁺ Teff intratumoral sequestration and synergized in cooperation with neutrophils in inducing cancer regression. 7HP349 intratumoral CD8⁺ Teff enrichment activity depended on CXCL12. We analyzed gene expression profiles using RNA from baseline and on treatment tumor samples of 14 melanoma patients. We identified baseline CXCL12 gene expression as possibly improving the likelihood or response to anti–CTLA-4 therapies. Our results provide a proof-of-principle demonstration that LFA-1 activation could convert a T cell–exclusionary TME to a T cell–enriched TME through mechanisms involving cooperation with innate immune cells.

Abstract 5010: Potentiating immune checkpoint blockade therapeutic efficacy using a small molecule activator of integrin cell adhesion receptors

Background: Immune checkpoint blockade (ICB) has therapeutic benefit in several human cancers, but in many patients, ICB - induced T cells do not infiltrate tumors, preventing clinical benefit. Intratumoral T cell accumulation requires firm adhesion mediated by the integrins very late antigen-4 (VLA-4) and lymphocyte function-associated antigen-1 (LFA-1) on activated T cells. The integrin class of cell adhesion receptors also play critical roles in multiple phases of tumor immune responses. Blocking the LFA-1 interaction with its ligand Intercellular adhesion molecule 1 (ICAM-1) abrogates CD8+ tumor infiltration after anti-CTLA4 therapy. Here, we evaluated the effect of an integrin activator, 7HP349, on promoting intratumoral T cell accumulation to potentiate CTLA-4 and PD-L1 checkpoint blockade anti-tumor activity.

Experimental Procedure: To evaluate the effect of 7HP349 in promoting ICB therapeutic activity, we combined 7HP349 with anti-CTLA-4 or anti-PD-L1 antibodies in preclinical murine models for melanoma and colon carcinoma.

Results: In cell adhesion assays, 7HP349 increased by >100-fold the number of VLA-4 or LFA-1 expressing T cells that bind to vascular cell adhesion molecule 1 (VCAM-1) and ICAM-1, respectively. 7HP349 facilitated chemo-attraction of T cells across matrices of VCAM-1 or ICAM-1, induced by the chemokine SDF-1α. In a PDL-1 negative B16/BL6 melanoma model, 7HP349 was dosed twice weekly at 1 mg/Kg intratumorally either alone as a single agent compared to vehicle control (13% vs 0%, p<0.01) or in combination with anti-CTLA-4 (44% vs 21%, p<0.01). After intraperitoneal administration, 7HP349 increased the complete response in combinations with anti-CTLA-4 (77% vs 27%, p<0.01). In addition, 7HP349 increased median survival in mice with CT-26 colon cancer when dosed either as a single agent versus control (21 vs 15 days, P<0.0012) or in combination with anti-PD-L1 (24 vs 21 days, P<0.02). 7HP349 may also increase the effectiveness of anti-CD137 without increasing liver toxicity. Levels of CD8 effector T cells (Teff) detected in tumor were significantly higher in mice treated with anti-CTLA-4 and 7HP349 than anti-CTLA-4 and vehicle. Some of these Teff showed specificity to p15E, an endogenous retroviral epitope expressed on B16. Mice treated with anti-CTLA-4 and 7HP349 showed increased depigmentation (vitiligo) suggesting immunity to melanocyte differentiation antigens.

Conclusion: 7HP349 described here represents a first-in-concept agent that positively regulate VLA-4 and LFA-1 function. Activation of integrin cell adhesion molecules with 7HP349 is a promising approach to enhance the anti-cancer activity of checkpoint blockade therapy with antibodies against CTLA-4 and PD-(L)1.

Citation Format: Yared Hailemichael, Peter Vanderslice, Robert V. Market, Ronald J. Biediger, Darren G. Woodside, Upendra K. Marathi, Willem W. Overwijk. Potentiating immune checkpoint blockade therapeutic efficacy using a small molecule activator of integrin cell adhesion receptors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5010.

Magnetic Resonance Imaging of Atherosclerotic Plaque at Clinically Relevant Field Strengths (1T) by Targeting the Integrin α4β1

Inflammation drives the degradation of atherosclerotic plaque, yet there are no non-invasive techniques available for imaging overall inflammation in atherosclerotic plaques, especially in the coronary arteries. To address this, we have developed a clinically relevant system to image overall inflammatory cell burden in plaque. Here, we describe a targeted contrast agent (THI0567-targeted liposomal-Gd) that is suitable for magnetic resonance (MR) imaging and binds with high affinity and selectivity to the integrin α4β1(very late antigen-4, VLA-4), a key integrin involved in recruiting inflammatory cells to atherosclerotic plaques. This liposomal contrast agent has a high T1 relaxivity (~2 × 10⁵ mM^-1s^-1 on a particle basis) resulting in the ability to image liposomes at a clinically relevant MR field strength. We were able to visualize atherosclerotic plaques in various regions of the aorta in atherosclerosis-prone ApoE^-/- mice on a 1 Tesla small animal MRI scanner. These enhanced signals corresponded to the accumulation of monocyte/macrophages in the subendothelial layer of atherosclerotic plaques in vivo, whereas non-targeted liposomal nanoparticles did not demonstrate comparable signal enhancement. An inflammatory cell-targeted method that has the specificity and sensitivity to measure the inflammatory burden of a plaque could be used to noninvasively identify patients at risk of an acute ischemic event.

Endothelin antagonists: substituted mesitylcarboxamides with high potency and selectivity for ET(A) receptors

We have previously disclosed the discovery of 2,4-disubstituted anilinothiophenesulfonamides with potent ET(A)-selective endothelin receptor antagonism and the subsequent identification of sitaxsentan (TBC11251, 1) as a clinical development compound (Wu et al. J. Med. Chem. 1997, 40, 1682 and 1690). The orally active 1 has demonstrated efficacy in a phase II clinical trial of congestive heart failure (Givertz et al. Circulation 1998, 98, Abstr. #3044) and was active in rat models of myocardial infarction (Podesser et al. Circulation 1998, 98, Abstr. #2896) and acute hypoxia-induced pulmonary hypertension (Chen et al. FASEB J. 1996, 10 (3), A104). We now report that an additional substituent at the 6-position of the anilino ring further increases the potency of this series of compounds. It was also found that a wide range of functionalities at the 3-position of the 2,4,6-trisubstituted ring increased ET(A) selectivity by approximately 10-fold while maintaining in vitro potency, therefore rendering the compounds amenable to fine-tuning of pharmacological and toxicological profiles with enhanced selectivity. The optimal compound in this series was found to be TBC2576 (7u), which has approximately 10-fold higher ET(A) binding affinity than 1, high ET(A)/ET(B) selectivity, and a serum half-life of 7.3 h in rats, as well as in vivo activity.

Rational design and synthesis of small molecule, non-oligosaccharide selectin inhibitors: (alpha-D-mannopyranosyloxy)biphenyl-substituted carboxylic acids

The calcium dependent E-selectin/sialyl Lewisx (sLex) interaction plays a key role in inflammation where it mediates the rolling of leukocytes prior to firm adhesion and extravasation from the vasculature. A model of E-selectin/sLex binding, along with previously reported structure-activity relationships of sLex-related oligosaccharide, was used in the rational design of non-oligosaccharide inhibitors of this pivotal interaction. A palladium-mediated biaryl-coupling (Suzuki) reaction was used as the key step to prepare a number of substituted biphenyls which were assayed for their ability to inhibit the binding of E-, P-, and L-selectin-IgG fusion proteins to sLex expressed on the surface of HL60 cells. Some of the compounds developed had greater in vitro potency than the parent sLex tetrasaccharide and are currently being evaluated in in vivo models of inflammation to select a candidate for clinical development.