Jennifer Green

Induction of Antigen-Specific Immunity with a Vaccine Targeting NY-ESO-1 to the Dendritic Cell Receptor DEC-205

Dendritic cell targeting safely leads to integrated humoral and cellular immunity when combined with TLR agonists in cancer patients. Start Spreading the News Dendritic cells are the matchmakers of the immune system: They introduce T cells to antigen, providing the right context for the T cell to react. However, tumor alters the nearby microenvironment in such a way as to block immune activation. Dhodapkar et al. attempt to overcome this inhibition by targeting a tumor antigen directly to dendritic cells. The authors tested a vaccine that consisted of a human antibody targeted to the dendritic cell receptor DEC-205 fused with the tumor antigen NY-ESO-1 in a cohort of patients with tumors refractory to other therapies. They also added Toll-like receptor ligands as adjuvants in a dose-escalating study. They found that treatment induced both humoral and cellular immunity in these patients, with no dose-limiting toxicities. What’s more, a subset of patients had either stable disease or disease regression, particularly those who had received immune checkpoint inhibitors. If these data can be reproduced in larger trials, this study suggests that targeting antigen to dendritic cells could be an additional avenue to boost the immune response to cancer. 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.

Phase I study utilizing a novel antigen-presenting cell-targeted vaccine with Toll-like receptor stimulation to induce immunity to self antigens in cancer patients

Purpose: The use of tumor-derived proteins as cancer vaccines is complicated by tolerance to these self-antigens. Tolerance may be broken by immunization with activated, autologous, ex vivo generated and antigen-loaded, antigen-presenting cells (APC); however, targeting tumor antigen directly to APC in vivo would be a less complicated strategy. We wished to test whether targeted delivery of an otherwise poorly immunogenic, soluble antigen to APC through their mannose receptors (MR) would induce clinically relevant immunity. Experimental Design: Two phase I studies were conducted with CDX-1307, a vaccine composed of human chorionic gonadotropin beta-chain (hCG-β) fused to an MR-specific monoclonal antibody, administered either locally (intradermally) or systemically (intravenously) in patients with advanced epithelial malignancies. An initial dose escalation of single-agent CDX-1307 was followed by additional cohorts of CDX-1307 combined with granulocyte-macrophage colony-stimulating factor (GM-CSF) and the Toll-like receptor (TLR) 3 agonist polyinosinic-polycytidylic acid (poly-ICLC) and TLR7/8 agonist resiquimod to activate the APC. Results: CDX-1307 induced consistent humoral and T-cell responses to hCG-β when coadministered with TLR agonists. Greater immune responses and clinical benefit, including the longest duration of stable disease, were observed with immunization combined with local TLR agonists. Immune responses were induced equally efficiently in patients with elevated and nonelevated levels of serum hCG-β. Antibodies within the serum of vaccinated participants had tumor suppressive function in vitro. Toxicity consisted chiefly of mild injection site reactions. Conclusions: APC targeting and activation induce adaptive immunity against poorly immunogenic self-antigens which has implications for enhancing the efficacy of cancer immunotherapy. Clin Cancer Res; 17(14); 4844–53. ©2011 AACR.

EMERGE: A Randomized Phase II Study of the Antibody-Drug Conjugate Glembatumumab Vedotin in Advanced Glycoprotein NMB–Expressing Breast Cancer

PURPOSE Glycoprotein NMB (gpNMB), a negative prognostic marker, is overexpressed in multiple tumor types. Glembatumumab vedotin is a gpNMB-specific monoclonal antibody conjugated to the potent cytotoxin monomethyl auristatin E. This phase II study investigated the activity of glembatumumab vedotin in advanced breast cancer by gpNMB expression. PATIENTS AND METHODS Patients (n = 124) with refractory breast cancer that expressed gpNMB in ≥ 5% of epithelial or stromal cells by central immunohistochemistry were stratified by gpNMB expression (tumor, low stromal intensity, high stromal intensity) and were randomly assigned 2:1 to glembatumumab vedotin (n = 83) or investigators choice (IC) chemotherapy (n = 41). The study was powered to detect overall objective response rate (ORR) in the glembatumumab vedotin arm between 10% (null) and 22.5% (alternative hypothesis) with preplanned investigation of activity by gpNMB distribution and/or intensity (Stratum 1 to Stratum 3). RESULTS Glembatumumab vedotin was well tolerated as compared with IC chemotherapy (less hematologic toxicity; more rash, pruritus, neuropathy, and alopecia). ORR was 6% (five of 83) for glembatumumab vedotin versus 7% (three of 41) for IC, without significant intertreatment differences for predefined strata. Secondary end point revealed ORR of 12% (10 of 83) versus 12% (five of 41) overall, and 30% (seven of 23) versus 9% (one of 11) for gpNMB overexpression (≥ 25% of tumor cells). Unplanned analysis showed ORR of 18% (five of 28) versus 0% (0 of 11) in patients with triple-negative breast cancer (TNBC), and 40% (four of 10) versus 0% (zero of six) in gpNMB-overexpressing TNBC. CONCLUSION Glembatumumab vedotin is well tolerated in heavily pretreated patients with breast cancer. Although the primary end point in advanced gpNMB-expressing breast cancer was not met for all enrolled patients (median tumor gpNMB expression, 5%), activity may be enhanced in patients with gpNMB-overexpressing tumors and/or TNBC. A pivotal phase II trial (METRIC [Metastatic Triple-Negative Breast Cancer]) is underway.

Phase I/II Study of the Antibody-Drug Conjugate Glembatumumab Vedotin in Patients With Locally Advanced or Metastatic Breast Cancer

PURPOSE Glycoprotein NMB (gpNMB), a novel transmembrane protein overexpressed in 40% to 60% of breast cancers, promotes metastases in animal models and is a prognostic marker of a poor outcome in patients. The antibody-drug conjugate glembatumumab vedotin consists of a fully human anti-gpNMB monoclonal antibody, conjugated via a cleavable linker to monomethyl auristatin E. Glembatumumab vedotin is generally well tolerated, with observed objective responses in advanced melanoma. This is, to our knowledge, the first study of glembatumumab vedotin in breast cancer. PATIENTS AND METHODS Eligible patients had advanced/metastatic breast cancer with at least two prior chemotherapy regimens, including taxane, anthracycline, and capecitabine. A standard 3+3 dose escalation was followed by a phase II expansion. Immunohistochemistry for gpNMB was performed retrospectively for patients with available tumor tissue. RESULTS Forty-two patients were enrolled. Dose-limiting toxicity (DLT) consisted of worsening neuropathy at 1.34 mg/kg. After excluding patients with baseline neuropathy more than grade 1, no DLT occurred through 1.88 mg/kg (the phase II dose). The phase II primary activity end point was met (12-week progression-free survival [PFS12] = 9 of 27 patients; 33%). Sixteen of 19 (84%) patients tested had gpNMB-positive tumors. At the phase II dose, median PFS was 9.1 weeks for all patients, 17.9 weeks for patients with triple-negative breast cancer (TNBC), and 18.0 weeks for patients with gpNMB-positive tumors. Two patients had confirmed partial responses; both had gpNMB-positive tumors and one had TNBC. CONCLUSION Glembatumumab vedotin has an acceptable safety profile. Preliminary evidence of activity in treatment-resistant metastatic breast cancer requires confirmation, such as the phase II randomized trial (EMERGE) that also examines the relationship between activity and gpNMB distribution/intensity.

Phase I/II Study of the Antibody-Drug Conjugate Glembatumumab Vedotin in Patients With Advanced Melanoma

PURPOSE The antibody-drug conjugate glembatumumab vedotin links a fully human immunoglobulin G2 monoclonal antibody against the melanoma-related glycoprotein NMB (gpNMB) to the potent cytotoxin monomethyl auristatin E. This study evaluated the safety and activity of glembatumumab vedotin in patients with advanced melanoma. PATIENTS AND METHODS Patients received glembatumumab vedotin every 3 weeks (schedule 1) in a dose escalation and phase II expansion at the maximum-tolerated dose (MTD). Dosing during 2 of 3 weeks (schedule 2) and weekly (schedule 3) was also assessed. The primary end points were safety and pharmacokinetics. The secondary end points included antitumor activity, gpNMB expression, and immunogenicity. RESULTS One hundred seventeen patients were treated using schedule 1 (n = 79), schedule 2 (n = 15), or schedule 3 (n = 23). The MTDs were 1.88, 1.5, and 1.0 mg/kg for schedules 1, 2, and 3, respectively. Grade 3/4 treatment-related toxicities that occurred in two or more patients included rash, neutropenia, fatigue, neuropathy, arthralgia, myalgia, and diarrhea. Three treatment-related deaths (resulting from pneumococcal sepsis, toxic epidermal necrolysis, and renal failure) occurred at doses exceeding the MTDs. In the schedule 1 phase II expansion cohort (n = 34), five patients (15%) had a partial response and eight patients (24%) had stable disease for ≥ 6 months. The objective response rate (ORR) was 2 of 6 (33%) for the schedule 2 MTD and 3 of 12 (25%) for the schedule 3 MTD. Rash was correlated with a greater ORR and improved progression-free survival. CONCLUSION Glembatumumab vedotin is active in advanced melanoma. The schedule 1 MTD (1.88 mg/kg once every 3 weeks) was associated with a promising ORR and was generally well tolerated. More frequent dosing was potentially associated with a greater ORR but increased toxicity.

CDX-1307: a novel vaccine under study as treatment for muscle-invasive bladder cancer

Cancer vaccines have demonstrated clinical benefit, however greater efficacy could be achieved by enhancing their immunogenicity. Owing to cancer vaccines depending on uptake and cross-presentation of tumor antigens by antigen-presenting cells (APCs), we hypothesized that greater immunogenicity would accompany strategies that direct antigen to APC-expressed mannose receptors, initiating a pathway increasing class I and II presentation to T cells. CDX-1307 consists of a human monoclonal antibody targeting the mannose receptor, fused to the human chorionic gonadotropin-β chain (hCG-β), a tumor antigen frequently expressed by epithelial cancers including bladder cancer. In Phase I studies of cancer patients, CDX-1307 was well tolerated and induced significant hCG-β-specific cellular and humoral immune responses when co-administered with GM-CSF and the Toll-like receptor agonists resiquimod and poly-ICLC. An ongoing Phase II trial evaluates CDX-1307 in patients with newly diagnosed, resectable, hCG-β-expressing bladder cancer, where low tumor burden and early intervention may provide greater potential for benefit.

Efficacy and safety of CDX-301, recombinant human Flt3L, at expanding dendritic cells and hematopoietic stem cells in healthy human volunteers.

Fms-like tyrosine kinase-3 ligand (Flt3L) uniquely binds the Flt3 (CD135) receptor expressed on hematopoietic stem cells (HSCs), early progenitor cells, immature thymocytes and steady-state dendritic cells (DCs) and induces their proliferation, differentiation, development and mobilization in the bone marrow, peripheral blood and lymphoid organs. CDX-301 has an identical amino-acid sequence and comparable biological activity to the previously tested rhuFlt3L, which ceased clinical development over a decade ago. This Phase 1 trial assessed the safety, pharmacokinetic, pharmacodynamic and immunologic profile of CDX-301, explored alternate dosing regimens and examined the impact of rhuFlt3L on key immune cell subsets. Thirty healthy volunteers received CDX-301 (1–75 μg/kg/day) over 5–10 days. One event of Grade 3 community-acquired pneumonia occurred. There were no other infections, dose-limiting toxicities or serious adverse events. CDX-301 resulted in effective peripheral expansion of monocytes, hematopoietic stem and progenitor cells and key subsets of myeloid DCs and plasmacytoid DCs, with no clear effect on regulatory T cells. These data from healthy volunteers support the potential for CDX-301, as monotherapy or in combination with other agents, in various indications including allogeneic HSC transplantation and immunotherapy, but the effects of CDX-301 will need to be investigated in each of these patient populations.