CTLA-4, a negative regulator of T cell function, was found to associate with the T cell receptor (TCR) complex ζ chain in primary T cells. The association of TCRζ with CTLA-4, reconstituted in 293 transfectants, was enhanced by p56 lck -induced tyrosine phosphorylation. Coexpression of the CTLA-4–associated tyrosine phosphatase, SHP-2, resulted in dephosphorylation of TCRζ bound to CTLA-4 and abolished the p56 lck -inducible TCRζ–CTLA-4 interaction. Thus, CTLA-4 inhibits TCR signal transduction by binding to TCRζ and inhibiting tyrosine phosphorylation after T cell activation. These findings have broad implications for the negative regulation of T cell function and T cell tolerance.

Immune-based therapies for cancer are generating substantial interest because of the success of immune checkpoint inhibitors. This study aimed to enhance anticancer immunity by exploiting the capacity of dendritic cells (DCs) to initiate T cell immunity by efficient uptake and presentation of endocytosed material. Delivery of tumor-associated antigens to DCs using receptor-specific monoclonal antibodies (mAbs) in the presence of DC-activating agents elicits robust antigen-specific immune responses in preclinical models. DEC-205 (CD205), a molecule expressed on DCs, has been extensively studied for its role in antigen processing and presentation. CDX-1401 is a vaccine composed of a human mAb specific for DEC-205 fused to the full-length tumor antigen NY-ESO-1. This phase 1 trial assessed the safety, immunogenicity, and clinical activity of escalating doses of CDX-1401 with the Toll-like receptor (TLR) agonists resiquimod (TLR7/8) and Hiltonol (poly-ICLC, TLR3) in 45 patients with advanced malignancies refractory to available therapies. Treatment induced humoral and cellular immunity to NY-ESO-1 in patients with confirmed NY-ESO-1–expressing tumors across various dose levels and adjuvant combinations. No dose-limiting or grade 3 toxicities were reported. Thirteen patients experienced stabilization of disease, with a median duration of 6.7 months (range, 2.4+ to 13.4 months). Two patients had tumor regression (~20% shrinkage in target lesions). Six of eight patients who received immune-checkpoint inhibitors within 3 months after CDX-1401 administration had objective tumor regression. This first-in-human study of a protein vaccine targeting DCs demonstrates its feasibility, safety, and biological activity and provides rationale for combination immunotherapy strategies including immune checkpoint blockade.

CD28 and CTLA-4 are related members of a family of T lymphocyte cell surface receptors that function to regulate T cell activation. We have found that the cytoplasmic domains of both CTLA-4 and CD28 can associate with members of the PP2A family of serine/threonine phosphatases. The association of PP2A with CD28 was negatively regulated by tyrosine phosphorylation of the CD28 cytoplasmic domain. Inhibition of PP2A activity in Jurkat leukemia T cells by treatment with okadaic acid or by expression of a dominant-negative mutant enhanced T cell activation induced by CD28 engagement. Interactions between cell surface receptors such as CTLA-4 and CD28 and serine/threonine phosphatases may represent a novel mechanism for modulating the intracellular signal transduction pathways associated with cell activation.

Eribulin demonstrated activity with manageable tolerability (including infrequent grade 3 and no grade 4 neuropathy) in heavily pretreated patients with MBC when dosed as a short IV infusion on days 1 and 8 of a 21-day cycle.