Antibodies In Solid Tumors Research Articles

A phase 1/2 study of the TORC1/2 inhibitor onatasertib combined with toripalimab in patients with advanced solid tumors.

2526 Background: Pre-clinical studies suggest synergistic activity of the combination of inhibitors of mTOR with a PD-1 antibody in solid tumors. Here we report updated results of a phase 1/2 open-label, dose escalation and expansion trial of the oral TORC1/2 inhibitor, onatasertib (ATG-008) in combination with toripalimab (tori), a PD-1 monoclonal antibody, in patients (pts) with advanced solid tumors. Methods: This study consists of dose escalation and dose expansion. The primary objective in the dose escalation phase was to evaluate safety and tolerability of onatasertib combined with tori, followed by a dose expansion phase to assess antitumor efficacy and verify the safety and tolerability profile of the combination therapy. Primary endpoints included maximum tolerated dose (MTD), recommended phase II dose (RP2D) and efficacy of the combination. Other endpoints included pharmacokinetics and exploratory biomarkers of drug activity. Prior PI3K/AKT/mTOR inhibitor therapy was excluded, regardless of PD-L1 expression. Onatasertib was administered orally once a day (QD) at three dose levels (15, 20 and 30mg) in combination with tori at the approved dose of 240 mg, once every 21 days (Q3W). Results: As of Oct 21, 2022 cut-off, 46 advanced solid tumor pts were enrolled with 10 pts in the dose escalation phase and 36 pts in the dose expansion phase. Median age was 53 years. Baseline ECOG scores were 0 (13 pts) and 1 (33 pts) with a median of 2 prior lines of therapy (0-7); 27 pts had stage IV disease. Twenty-one cervical cancer (CC) pts were enrolled in total with the similar baseline characteristics. No dose-limiting toxicity was reported in dose escalation phase. The study did not reach MTD. Forty-five pts (97.8%) had ≥ 1 TEAEs; 32 (69.6%) pts had grade ≥ 3 TEAEs. The most common grade ≥ 3 TEAEs included lymphocyte count decreased (23.9%), rash (19.6%) and hyperglycemia (10.9%). The RP2D for onatasertib was determined to be 15 mg in combination with the recommended dose of tori. Among the 46 treated pts, ORR was 26.1% (12/46, all confirmed), and DCR was 73.9%. In 21 pts with CC, ORR was 52.4%, including 1 CR and 10 PR, and DCR was 90.5%. One CC pt with negative PD-L1 expression achieved CR and remains on treatment after 883 days. The ORR was 75% (6/8) and 41.7% (5/12) for CC pts with PD-L1 positive and negative expressions, respectively. One CC pt with prior anti-PD-1 therapy also reached PR. Another PR was achieved in nasopharyngeal carcinoma (NPC) for over 2 years. Median PFS in all treated pts and CC cohort was 4.3 months(m) and 7.2 m, respectively. Pharmacokinetic profiles of ATG-008 in combination with PD-1 antibody were similar to ATG-008 monotherapy, across Asia Pacific and U.S. patient populations. Conclusions: Onatasertib in combination with tori is tolerable with encouraging response rate and disease stabilisation in pts with advanced solid tumors, especially in CC pts. Expansion enrolment for CC and NPC is ongoing. Clinical trial information: NCT04337463 .

Mechanistically Weighted Metric to Predict In Vivo Antibody-Receptor Occupancy: An Analytical Approach.

In situ clinical measurement of receptor occupancy (RO) is challenging, particularly for solid tumors, necessitating the use of mathematical models that predict tumor receptor occupancy to guide dose decisions. A potency metric, average free tissue target to initial target ratio (AFTIR), was previously described based on a mechanistic compartmental model and is informative for near-saturating dose regimens. However, the metric fails at clinically relevant subsaturating antibody doses, as compartmental models cannot capture the spatial heterogeneity of distribution faced by some antibodies in solid tumors. Here we employ a partial differential equation (PDE) Krogh cylinder model to simulate spatiotemporal receptor occupancy and derive an analytical solution, a mechanistically weighted global AFTIR, that can better predict receptor occupancy regardless of dosing regimen. In addition to the four key parameters previously identified, a fifth key parameter, the absolute receptor density (targets/cell), is incorporated into the mechanistic AFTIR metric. Receptor density can influence equilibrium intratumoral drug concentration relative to whether the dose is saturating or not, thereby influencing the tumor penetration depth of the antibody. We derive mechanistic RO predictions based on distinct patterns of antibody tumor penetration, presented as a global AFTIR metric guided by a Thiele Modulus and a local saturation potential (drug equivalent of binding potential for positron emissions tomography imaging) and validate the results using rigorous global and local sensitivity analysis. This generalized AFTIR serves as a more accurate analytical metric to aid clinical dose decisions and rational design of antibody-based therapeutics without the need for extensive PDE simulations. SIGNIFICANCE STATEMENT: Determining antibody-receptor occupancy (RO) is critical for dosing decisions in pharmaceutical development, but direct clinical measurement of RO is often challenging and invasive, particularly for solid tumors. Significant efforts have been made to develop mathematical models and simplified analytical metrics of RO, but these often require complex computer simulations. Here we present a mathematically rigorous but simplified analytical model to accurately predict RO across a range of affinities, doses, drug, and tumor properties.

Preliminary results from a phase 1/2 study of co-stimulatory bispecific PSMAxCD28 antibody REGN5678 in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC).

154 Background: Pts with mCRPC have a poor prognosis with limited treatment options, including minimal response to immunotherapies. REGN5678 is a first-in-class, full-length anti-PSMAxCD28 bispecific costimulatory antibody designed to target prostate cancer cells and enhance T-cell activation. We report preliminary results from the dose escalation part of a first-in-human, open-label, Phase 1/2 study (NCT03972657) examining REGN5678 in combination with cemiplimab, a PD-1 blocking antibody. Methods: Pts with mCRPC had received ≥2 lines of systemic therapy in the metastatic and/or castration-resistant setting, including ≥1 second-generation anti-androgen. Pts received REGN5678 weekly at dose levels [DL] 0.1–300 mg, initially as monotherapy for 3 weeks, followed by combination with cemiplimab (350 mg Q3W) until progression or toxicity. Primary objectives are safety, tolerability, and pharmacokinetics. Preliminary efficacy measurements include decline in prostate-specific antigen (PSA) from the start of combination treatment and radiographic response from baseline. Results: At the data cutoff (DCO; July 27 2022), 35 pts had been treated. Treatment-emergent adverse events (TEAEs) ≥Grade (G)3 occurred in 54% (19/35) of pts. Cytokine release syndrome occurred in 6 pts (all G1) and there were 2 dose-limiting toxicities (both G3): pain (at 1 mg) and Guillain-Barré syndrome (at 300 mg). 4 pts (11%) experienced a ≥G3 immune-mediated adverse event (imAE; at DLs 30–300 mg). REGN5678 exposure was non-linear over the tested DLs (more than dose proportional). There were minimal signs of efficacy at lower DLs (REGN5678 0.1–10 mg), with only 1/16 pts showing a PSA decline (of 21%). More PSA declines occurred at higher DLs: 1/4 pts at 30 mg (a PSA decline of 100%), 3/8 at 100 mg (>99%, 44%, 22%), and 3/4 at 300 mg (>99%, 99%, 82%). Notably, all ≥G3 imAEs occurred in pts with PSA declines. Among pts with measurable disease and ≥1 on-treatment scan, radiographic response per RECIST 1.1 occurred in 1/3 pts at 30 mg (complete response), 1/4 at 100 mg (unconfirmed partial response [PR]), and 1/1 at 300 mg (PR confirmed after DCO). Conclusions: Preliminary data on REGN5678 plus cemiplimab in pts with mCRPC provide first evidence of clinical activity of a CD28 co-stimulatory bispecific antibody in solid tumors. Clinical activity was observed at DLs 30–300 mg. ≥G3 imAEs occurred in pts with PSA declines, suggesting a possible association. The study is ongoing to determine the maximum tolerated and recommended Phase 2 doses. Clinical trial information: NCT03972657 . [Table: see text]

193P CLAUDIN-1 targeting antibodies in solid tumors: From ALE.C04 to CLAUDIN-1 oncology platform

Claudin 1 (CLDN1) is a protein confined within the normal epithelial tight junctions of different tissues. Upon malignant transformation, CLDN1 is overxpressed and epitopes become exposed outside the tight junctions (non-Junctional CLDN1). ALE.C04 is a highly specific humanized monoclonal antibody that recognizes a unique CLDN1 exposed epitope in different solid tumors.

Towards Photodynamic Image-Guided Surgery of Head and Neck Tumors: Photodynamic Priming Improves Delivery and Diagnostic Accuracy of Cetuximab-IRDye800CW.

Fluorescence image-guided surgery (IGS) using antibody conjugates of the fluorophore IRDye800CW have revolutionized the surgical debulking of tumors. Cetuximab, an anti-epidermal growth factor receptor (EGFR) monoclonal antibody, conjugated to IRDye800CW (Cet-IRDye800) is the first molecular targeted antibody probe to be used for IGS in head and neck cancer patients. In addition to surgical debulking, Cetuximab-targeted photodynamic therapy (photoimmunotherapy; PIT) is emerging in the clinic as a powerful modality for head and neck tumor photodestruction. A plethora of other photoactivable agents are also in clinical trials for photodynamic-based therapies of head and neck cancer. Considering the vascular and stromal modulating effects of sub-therapeutic photodynamic therapy, namely photodynamic priming (PDP), this study explores the potential synergy between PDP and IGS for a novel photodynamic image-guided surgery (P-IGS) strategy. To the best of our knowledge, this is the first demonstration that PDP of the tumor microenvironment can augment the tumor delivery of full-length antibodies, namely Cet-IRDye800. In this study, we demonstrate a proof-of-concept that PDP primes orthotopic FaDu human head and neck tumors in mice for P-IGS by increasing the delivery of Cet-IRDye800 by up to 138.6%, by expediting its interstitial accumulation by 10.5-fold, and by increasing its fractional tumor coverage by 49.5% at 1 h following Cet-IRDye800 administration. Importantly, PDP improves the diagnostic accuracy of tumor detection by up to 264.2% with respect to vicinal salivary glands at 1 h. As such, PDP provides a time-to-surgery benefit by reducing the time to plateau 10-fold from 25.7 h to 2.5 h. We therefore propose that a pre-operative PDP regimen can expedite and augment the accuracy of IGS-mediated surgical debulking of head and neck tumors and reduce the time-to-IGS. Furthermore, this P-IGS regimen, can also enable a forward-looking post-operative protocol for the photodestruction of unresectable microscopic disease in the surgical bed. Beyond this scope, the role of PDP in the homogenous delivery of diagnostic, theranostic and therapeutic antibodies in solid tumors is of considerable significance to the wider community.

A phase 1/2 study of onatasertib, a dual TORC1/2 inhibitor, combined with the PD-1 antibody toripalimab in patients with advanced solid tumors (TORCH-2).

2610 Background: Pre-clinical studies suggest synergistic activity of the combination of inhibitors of mTOR with a PD-1 antibody in solid tumors. Here we report initial results of a phase 1/2 open-label, dose escalation and expansion trial of the oral TORC1/2 inhibitor, onatasertib (ATG-008) in combination with toripalimab (tori), a PD-1 monoclonal antibody, in patients (pts) with advanced solid tumors (NCT04337463). Methods: This study consists of two phases: dose escalation and dose expansion. The primary objective in the dose escalation phase was to evaluate safety and tolerability of onatasertib combined with tori, followed by a dose expansion phase to assess antitumor efficacy and verify the safety and tolerability profile of the combination therapy. Primary endpoints included maximum tolerated dose (MTD), recommended phase II dose (RP2D) and efficacy of the combination. Other endpoints included pharmacokinetics, and exploratory biomarkers of drug activity. Prior check point (anti-PD-1, anti-PD-L1, CTLA-4), mTOR and/or PI3K/AKT/mTOR inhibitor therapy was excluded, regardless of PD-L1 expression. Onatasertib was administered orally once a day (QD) at three dose levels (15, 20 and 30mg) in combination with tori at the approved dose of 240 mg, once every 21 days (Q3W). Efficacy assessments are reported based on RECIST1.1 criteria. Results: As of Dec 20, 2021 cut-off, 28 advanced solid tumor pts were enrolled in the study with 10 pts in the dose escalation phase and 18 pts in the dose expansion phase. Median age was 52 years. Baseline ECOG scores were 0 (4 pts) and 1 (24 pts) with a median of 2 prior lines therapy (0-7), 21 pts had stage IV disease. No dose-limiting toxicities were reported in dose escalation phase. The study did not reach MTD. All pts had ≥ 1 TEAEs; 19 (67.9%) pts had grade ≥ 3 TEAEs. The most common grade ≥ 3 TEAEs included lymphocyte count decreased (21.4%), rash (14.3%) and hyperglycemia (10.7%). AEs lead to discontinuation in 2 pts (7.1%). The RP2D for onatasertib was determined to be 15-20 mg in combination with the recommended dose of tori. Among the 21 efficacy evaluable (EE) pts, the ORR was 28.6% (6 pts, 5 confirmed) and DCR was 71.4% (15 pts). In 5 EE pts with cervical cancer, 1 complete response (CR) and 3 partial responses (PR) were observed (all confirmed). One cervical cancer pt with negative PD-L1 expression achieved CR and remains on treatment after 580 days. Two other PRs were seen (one nasopharyngeal carcinoma, one ovarian carcinoma). Median progression free survival (PFS) in the whole cohort was 3.52 months and 18-month PFS rate was 31.2%. Conclusions: Onatasertib in combination with tori is tolerable with encouraging response rates and disease stabilisation in subjects with advanced solid tumors, especially in cervical cancer. Expansion enrolment for cervical cancer is ongoing and updated information will be presented. Clinical trial information: NCT04337463.

Phase I clinical trial of NEO-201, an anti-tumor-associated CEACAM-5/6 monoclonal antibody in solid tumors.

2531 Background: NEO201 is a humanized IgG1 monoclonal antibody generated against tumor-associated antigens from colorectal cancer which binds specifically to tumor-associated CEACAM-5 and CEACAM-6 variants without binding CECAM 5/6 on normal epithelial tissues. NEO-201 reactivity is positive in the majority of adenocarcinomas including colon (85%), pancreas (86%), lung (79%), and breast (53%). Preclinical data showed that NEO-201 exerts anti-tumor activity through antibody dependent cellular cytotoxicity and complement dependent cytotoxicity. Here we present outcomes from a phase I trial of NEO-201 in advanced solid tumors (NCT03476681). Methods: This was a classic 3+3 dose escalation trial, with cohort expansion at the RP2D. NEO-201 was administered intravenously every two weeks in a 28-day cycle. The primary objective was to assess the MTD/RP2D of NEO-201 in patients with advanced solid tumors. The secondary objective was to assess the preliminary antitumor activity and exploratory objectives assessed pharmacokinetics and the effect of NEO-201 administration on immunologic parameters and possible relationships with response. Of 17 patients enrolled, 11 had colorectal, 4 had pancreatic and 2 had breast cancer. 4 patients received NEO-201 at dose level (DL) 1 (1 mg/kg), 6 patients at DL 1.5 (1.5 mg/kg) and 7 patients at dose DL 2 (2 mg/kg). Results: At the time of data cutoff, all patients had discontinued therapy. 11 of 14 evaluable patients discontinued due to disease progression and 3 patients discontinued due to DLT (grade 4 febrile neutropenia and prolonged neutropenia, each in 1/6 patients at DL2, and grade 3 febrile neutropenia in 1/6 patients at DL 1.5). Most common grade 3/4 toxicities were neutropenia (94%), white blood cell decrease (59%), lymphocyte decrease (29%), and febrile neutropenia (24%). Protocol was modified to allow administration of G-CSF and based on safety and PK data the RP2D was established as 1.5mg/Kg. Median number of doses received was 4.7. 13 subjects were able to undergo disease assessment after two cycles. The best response observed was stable disease (SD) in 5/9 evaluable patients with colorectal cancer. Minor CA-19-9 reductions were observed in two pancreatic cancer patients at DL 1.5. Correlative endpoints revealed that all patients enrolled in the trial expressed NEO-201 target antigen on their tumor tissue. Analysis of soluble factors in serum revealed that a high level of soluble MICA at baseline was correlated with a downregulation of NK cell activation markers and progressive disease. Unexpectedly, flow cytometry showed that NEO-201 also binds to circulating T regulatory cells and depleted these cells especially in patients with SD. Conclusions: NEO-201 was safe and well tolerated at the MTD of 1.5 mg/kg. Depletion of T regulatory cells suggests that the combination of NEO-201 with immune checkpoint inhibitor should be tested in future clinical trials. Clinical trial information: NCT03476681.

A patch of positively charged residues regulates the efficacy of clinical DR5 antibodies in solid tumors.

SUMMARYReceptor clustering is the first and critical step to activate apoptosis by death receptor-5 (DR5). The recent discovery of the autoinhibitory DR5 ectodomain has challenged the long-standing view of its mechanistic activation by the natural ligand Apo2L. Because the autoinhibitory residues have remained unknown, here we characterize a crucial patch of positively charged residues (PPCR) in the highly variable domain of DR5. The PPCR electrostatically separates DR5 receptors to autoinhibit their clustering in the absence of ligand and antibody binding. Mutational substitution and antibody-mediated PPCR interference resulted in increased apoptotic cytotoxic function. A dually specific antibody that enables sustained tampering with PPCR function exceptionally enhanced DR5 clustering and apoptotic activation and distinctively improved the survival of animals bearing aggressive metastatic and recurrent tumors, whereas clinically tested DR5 antibodies without PPCR blockade function were largely ineffective. Our study provides mechanistic insights into DR5 activation and a therapeutic analytical design for potential clinical success.

Transient Competitive Inhibition Bypasses the Binding Site Barrier to Improve Tumor Penetration of Trastuzumab and Enhance T-DM1 Efficacy.

Poor penetration of mAbs in solid tumors is explained, in part, by the binding site barrier hypothesis. Following extravasation, mAbs rapidly bind cellular antigens, leading to the observation that, at subsaturating doses, therapeutic antibody in solid tumors localizes around tumor vasculature. Here we report a unique strategy to overcome the binding site barrier through transient competitive inhibition of antibody-antigen binding. The anti-trastuzumab single domain antibody 1HE was identified through in vitro binding assays as a model inhibitor. Coadministration of 1HE did not alter the plasma pharmacokinetics of trastuzumab or ado-trastuzumab emtansine (T-DM1) in vivo. Administration of 1HE alone was rapidly eliminated with a terminal plasma half-life of 1.2 hours, while coadministrations of 1HE with trastuzumab had a terminal half-life of 56 hours. In mice harboring SKOV3 xenografts, coadministration of 1HE with trastuzumab led to significant increases in both penetration of trastuzumab from vasculature and the percentage of tumor area that stained positive for trastuzumab. 1HE coadministered with a single dose of T-DM1 to NCI-N87 xenograft-bearing mice significantly enhanced T-DM1 efficacy, increasing median survival. These results support the hypothesis that transient competitive inhibition can improve therapeutic antibody distribution in solid tumors and enhance antibody efficacy. SIGNIFICANCE: This study describes the development of a transient competitive inhibition strategy that enhances the tumor penetration and efficacy of anticancer antibodies.See related commentary by van Dongen, p. 3956.

Anti-LDLR modified TPZ@Ce6-PEG complexes for tumor hypoxia-targeting chemo-/radio-/photodynamic/photothermal therapy.

Hypoxia, a state of low oxygen tension in solid tumors, is not only closely correlated with resistance to both radiotherapy and chemotherapy, but also associated with poor prognosis of tumors and regional lymph node status. Herein, based on the analysis of cell samples from tumor patients, low-density lipoprotein receptor (LDLR) was found to be overexpressed on the surface of hypoxic tumor cell membranes, and confirmed to be an effective hypoxia marker through specific binding with anti-LDLR antibody in solid tumors. In addition, using the special therapeutic microenvironment of hypoxia, tirapazamine (TPZ, which can be used as both a hypoxia-activated chemotherapy prodrug and radiotherapy sensitizer) was integrated with PEGylated photosensitizer chlorin e6 (Ce6-PEG) by self-assembly, and anti-LDLR was then modified on the surface to form tumor hypoxia-targeting multifunctional nanoparticles (CPTA). CPTA possesses a multimodal antitumor effect via a simultaneous photothermal therapy (PTT)/photodynamic therapy (PDT) effect generated by Ce6, and chemotherapy/radiotherapy actions sensitized by TPZ. It is noteworthy that tumor oxygen was consumed in the process of PDT and the hypoxia was subsequently exacerbated, which can greatly increase the TPZ-sensitized chemotherapy and lead to a synergistic antitumor effect. Both in vitro and in vivo experiments demonstrated that CPTA possesses an excellent therapeutic effect through PTT, PDT, and TPZ sensitized radiotherapy and chemotherapy. This hypoxic tumor targeting synergetic therapeutic strategy has great potential for future clinical transformation.

Abstract 497: Characterization of TIGIT expression using MultiOmyxTM hyperplexed immunofluorescence assay in solid tumors

Abstract TIGIT (T cell immunoreceptor with Ig and ITIM domains) is a recently identified immune-receptor that is expressed on T cells, natural killer (NK) cells and NKT cells. TIGIT has emerged as an important coinhibitory receptor. TIGIT expression on CD8+ tumor infiltrating lymphocytes (TILs) has been shown to be upregulated in solid cancers such as melanoma, colon cancer, and NSCLC and have been associated with a dysfunctional phenotype in TILs. TIGIT can also be activated on a subset of Regulatory T cells (Tregs) and may be critical in driving CD8+ T cell dysfunction. A second mechanism in which TIGIT inhibits immunosurveillance is through both competition and direct inhibition of CD226, impairing its ability to activate immunosurveillance. TIGIT has also been reported to inhibit T cell responses indirectly by triggering CD155 expression in dendritic cells (DCs), thereby preventing DC maturation. These findings render the TIGIT pathway as an attractive candidate for cancer immunotherapy In this study, we seek to use MultiOmyx hyperplexed immunofluorescence (IF) assay to exploit this new pathway and characterize the TIGIT expression in a total of 20 melanoma and NSCLC samples. The cancer FFPE slides will be stained with a 13-marker panel including TIGIT, CD226, CD155, CD3, CD4, CD8, FOXP3, CD56, CD45, CD11b, CD11c, PD1, LAG3, TIM3 and PanCK. This panel will enable the detection of TIGIT, CD226 and CD115 expression in the Melanoma and NSCLC samples. The TIGIT expression will be further characterized on different TILs including CD4+ helper T cells, CD8+ cytotoxic T cells, Tregs and NK cells. Using the MultiOmyx proprietary algorithm, we can quantify different subtypes of TIGIT expressing cells and measure the distance of different TIGIT expressing cells to the tumor. Increased expression of TIGIT and PD1 has been demonstrated in NSCLC and melanoma. Moreover, TIGIT+ Tregs have been reported to upregulate TIM-3 expression in mice tumor models. In this study, we will also evaluate the expression of TIGIT in conjunction with other coinhibitory receptors such as PD1, LAG3 and TIM3. The percentage of TILs that co-express TIGIT/PD1, TIGIT/LAG3 and TIGIT/TIM3 will be quantified and analyzed. Leveraging TIGIT in combination with other immune therapy may achieve more robust clinical outcomes. There are currently multiple phase I clinical trials using TIGIT monoclonal antibody (for instance, BMS-986207 by Bristol-Myers Squibb and MTIG7192A by Genetech) in combination with anti PD1/PDL1 antibodies in solid tumors. Our data can help provide more insight into how TIGIT modulate antitumor immunity in melanoma and NSCLC tumors. And the findings in this study can also be used to understand the synergistic effects between TIGIT and other coinhibitory receptors and help identify the additional opportunity for combination immunotherapy using checkpoint inhibitors. Citation Format: Qingyan Au, Arezoo Hanifi, Erinn Parnell, Judy Kuo, Eric Leones, Flora Sahafi, Kathy Pham, RaghavKrishna Padmanabhan, Nicholas Hoe, Josette William. Characterization of TIGIT expression using MultiOmyxTM hyperplexed immunofluorescence assay in solid tumors [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 497.

Association of frequent amplification of chromosome 11q13 in esophageal squamous cell cancer with clinical benefit to immune check point blockade.

4036 Background: Esophageal squamous cell carcinoma (ESCC) is the predominant histological subtype of esophageal cancer in South America and East Asian countries and remains an unmet medical need worldwide. Previous studies have shown the efficacy of programmed cell death 1 (PD-1) targeted therapy in a subset of patients with metastatic ESCC. However, robust predictive biomarkers to PD-1 antibody-based immunotherapy remain undefined. Methods: Patients included in this analysis were part of multi-center, phase Ib/II trial (NCT02915432) evaluating the safety and activity of toripalimab, a humanized PD-1 antibody in solid tumors. To identify molecular determinants of response, we performed whole exome sequencing (WES), messenger RNA sequencing and immunohistochemistry on patients’ samples and evaluated genomic and transcriptional biomarkers, PD-L1 expression and tumor mutational burden (TMB) for correlation with clinical efficacy. Results: Sixty advanced chemo-refractory ESCC patients were enrolled and 59 were treated with toripalimab. 94.9% (56/59) patients experienced at least one treatment related adverse event after 16 months; mostly grade 1 or grade 2. Treatment-related grade 3 or higher AEs occurred in 30.5% (18/59) of subjects. By the data cutoff date, 11 (18.6%; 95%CI 9.7 to 30.9) patients achieved an objective response, while the disease control rate was 47.5% (95%CI 34.3 to 60.9). Copy number analysis identified 24 out of 50 (48%) patients with amplifications of chromosome 11q13 region, which was consistent with elevated mRNA expression of amplified genes, including CCND1(Cyclin D1) and fibroblast growth factor family members ( FGF3/4/19). Patients without 11q13 amplification, had significantly better objective response rate (ORR 30.8% versus 4.2%, p= 0.024) and progression free survival (3.7 versus 2.0 months, HR = 0.47 [95%CI 0.24 to 0.91], p= 0.025) when compared with 11q13 amplified individuals. In contrast, patients with high TMB (≥12 Mutations/Mb; 11/47, 23.4%) or positive PD-L1 expression (TC or IC 1%; 19/57, 33.3%) showed no significant advantage in ORR or survival. Conclusions: Toripalimab has demonstrated a manageablesafety profile and promising anti-tumor activity in chemo-refractory ESSC patients. Genomic amplification of 11q13 region may serve as a negative predictive marker for advanced ESSC patients receiving anti-PD-1 based immunotherapy. Further interrogation of putative resistance genes that lie within this region is under study. Clinical trial information: NCT02915432.

Abstract 1754: Smac mimetics APG-1387 synergizes with immune checkpoint inhibitors in preclinical models

Abstract APG-1387 is a novel, SMAC-mimetic, small molecule inhibitor for inhibitor of apoptosis proteins (IAPs). IAPs are a class of proteins which negatively regulate caspases and apoptosis. The IAP proteins are frequently dysregulated in many cancers and have been suggested as contributing to apoptosis-resistance of cancer cells to a variety of anticancer drugs. DNA amplification of the cellular IAP-1 (cIAP-1) and cellular IAP-2 (cIAP-2) genes (BIRC2 and BIRC3, respectively) has been observed in various human cancer types, including lung cancer, pancreatic cancer, and liver carcinoma. Dysregulation of IAP proteins has also been frequently observed at the protein level in multiple cancer cell lines and tumor samples. IAPs contribute to tumor cell survival, chemo-resistance, disease progression, and poor prognosis. In addition, IAPs play an important role in immune regulation. For example, IAPs regulate ubiquitin (Ub)-dependent pathways that modulate innate immune signaling via activation of nuclear factor κB (NF-κB). Due to their significant biological functions in cell death and immune responses, IAPs have been emerging as drug targets in a wide range of malignancies. Several IAP inhibitors have been developed and their clinical benefits are currently in investigation in multiple clinical trials in both single agent and combination regimen with immune checkpoint inhibitors. APG-1387 has been developed as a novel drug candidate targeting IAPs. Mechanistically, in both cancer cells and xenograft tumors, APG-1387 induces degradation of cIAP-1 and XIAP proteins, as well as caspase-3 activation and PARP cleavage, which leads to apoptosis. Anti-proliferative and anti-tumor activities of APG-1387 have been well demonstrated in a panel of cancer cell lines and xenograft tumor models. In this study, we explored the synergistic effect of APG-1387 in combination therapy with immune checkpoint inhibitors. We found that APG-1387 enhanced human PBMC co-stimulation of anti-CD3 and anti-CD28, and T cell proliferation in vitro. In syngeneic tumor tissues, the combination treatment with APG-1387 and anti-PD-1 antibody led to an increase in CD3+ and CD8+ T cell populations and a decrease in Treg cell population. Synergistic effect of the combination was further demonstrated in syngeneic tumor models. Taken together, our results suggest that the treatment with APG-1387 may enhance the effect of anti-PD-1 antibody therapy. Consequently, APG-1387 has been approved by FDA for phase I clinical trials as single agent and in combination with anti-PD-1 antibody in solid tumors. Citation Format: Wentao Pan, Douglas D. Fang, Guangfeng Wang, Miaoyi Wu, Yingfeng Li, Keji Lian, Dingxiong Cheng, Yanhui Kong, Guoqin Zhai, Ming Guo, Shaomeng Wang, Dajun Yang, Yifan Zhai. Smac mimetics APG-1387 synergizes with immune checkpoint inhibitors in preclinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1754.

Immunotherapy Against Head and Neck Cancer Stem Cells

Immunotherapy against head and neck cancer stem cells Immunologic therapies like antibodies in solid tumors like squamous cell cancer of the head and neck are administered either alone or in combination with radiation and chemotherapy. Despite some respectable successes, the effect of this therapy reaches its limits due the ability of the tumor to escape the immune system. Cancer stem cells seem to play an important role in this process due to their intrinsic resistance to conventional therapy and the ability to regenerate tumor heterogeneity. This way they substantially contribute to the formation of recurrences and metastases. Therefore, future immunotherapies should target specifically this subpopulation, possibly in combination with other therapeutic modalities. In this review the immunologic features of cancer stem cells and their potential as target for immunotherapies is summarized.

KIR Genes and Their Ligands Predict the Response to Anti-EGFR Monoclonal Antibodies in Solid Tumors.

Killer-cell immunoglobulin-like receptors (KIRs) regulate the killing function of natural killer cells, which play an important role in the antibody-dependent cell-mediated cytotoxicity response exerted by therapeutic monoclonal antibodies (mAbs). However, it is unknown whether the extensive genetic variability of KIR genes and/or their human leukocyte antigen (HLA) ligands might influence the response to these treatments. This study aimed to explore whether the variability in KIR/HLA genes may be associated with the variable response observed to mAbs based anti-epidermal growth factor receptor (EGFR) therapies. Thirty-nine patients treated with anti-EGFR mAbs (trastuzumab for advanced breast cancer, or cetuximab for advanced colorectal or advanced head and neck cancer) were included in the study. All the patients had progressed to mAbs therapy and were grouped into two categories taking into account time to treatment failure (TTF ≤6 and ≥10 months). KIR genotyping (16 genetic variability) was performed in genomic DNA from peripheral blood by PCR sequence-specific primer technique, and HLA ligand typing was performed for HLA-B and -C loci by reverse polymerase chain reaction sequence-specific oligonucleotide methodology. Subjects carrying the KIR/HLA ligand combinations KIR2DS1/HLAC2C2-C1C2 and KIR3DS1/HLABw4w4-w4w6 showed longer TTF than non-carriers counterparts (14.76 vs. 3.73 months, p < 0.001 and 14.93 vs. 4.6 months, p = 0.005, respectively). No other significant differences were observed. Two activating KIR/HLA ligand combinations predict better response of patients to anti-EGFR therapy. These findings increase the overall knowledge on the role of specific gene variants related to responsiveness to anti-EGFR treatment in solid tumors and highlight the importance of assessing gene polymorphisms related to cancer medications.

Toxicity profile of approved anti-PD-1 monoclonal antibodies in solid tumors: a systematic review and meta-analysis of randomized clinical trials.

PurposeNivolumab and pembrolizumab are antibodies against the programmed-death-receptor- 1 (PD-1) which are associated with distinct immune related adverse effects (AEs). This meta-analysis of randomized clinical trials aims to summarize current knowledge regarding the toxicity profile of these agents.MethodsPubMed search was conducted in February of 2016. The randomized trials needed to have at least one of the study arms consisting of nivolumab or pembrolizumab monotherapy and a control arm containing no anti-PD-1 therapy. Data were analyzed using random effects meta-analysis for risk ratios. Heterogeneity across studies was analyzed using Q and I2 statistics.ResultsNine randomized trials and 5,353 patients were included in our meta-analysis. There was evidence of significant heterogeneity between studies. The pooled relative risk (RR) for treatment-related all grade AEs and grade 3/4 AEs was 0.88 (95% CI 0.81-0.95;P=0.002) and 0.39 (95% CI 0.29-0.53; P<0.001) respectively favoring anti-PD-1 therapy versus standard of care approach. The RR of treatment-related death was 0.45 (95% CI 0.19-1.09; P=0.076). Patients treated with PD-1 inhibitors had an increased risk of hyperthyroidism [RR of 3.44 (95% CI 1.98-5.99; P<0.001)] and hypothyroidism [RR of 6.79 (95% CI 3.10-14.84; P<0.001)]. All grade pruritus and vitiligo were also more common among these patients. The pooled absolute risks of pneumonitis and hypophysitis were 2.65% and 0.47% respectively.ConclusionApproved PD-1 inhibitors are well tolerated, associated with significant low risk of severe treatment-related AEs and increased risk of thyroid dysfunction, pruritus, and vitiligo.

Toxicity profile of approved anti-PD1 monoclonal antibodies in solid tumors: A systematic review and meta-analysis of randomized clinical trials.

3064Background: Clinical trials supported the FDA approval of anti-PD1 antibodies nivolumab and pembrolizumab for treatment of advanced melanoma, renal cell carcinoma, and non-small cell lung cance...

Influence of Affinity and Antigen Internalization on the Uptake and Penetration of Anti-HER2 Antibodies in Solid Tumors

Antibody drugs are widely used in cancer therapy, but conditions to maximize tumor penetration and efficacy have yet to be fully elucidated. In this study, we investigated the impact of antibody binding affinity on tumor targeting and penetration with affinity variants that recognize the same epitope. Specifically, we compared four derivatives of the C6.5 monoclonal antibody (mAb), which recognizes the same HER2 epitope (monovalent K(D) values ranging from 270 to 0.56 nmol/L). Moderate affinity was associated with the highest tumor accumulation at 24 and 120 hours after intravenous injection, whereas high affinity was found to produce the lowest tumor accumulation. Highest affinity mAbs were confined to the perivascular space of tumors with an average penetration of 20.4 ± 7.5 μm from tumor blood vessels. Conversely, lowest affinity mAbs exhibited a broader distribution pattern with an average penetration of 84.8 ± 12.8 μm. In vitro internalization assays revealed that antibody internalization and catabolism generally increased with affinity, plateauing once the rate of HER2 internalization exceeded the rate of antibody dissociation. Effects of internalization and catabolism on tumor targeting were further examined using antibodies of moderate (C6.5) or high-affinity (trastuzumab), labeled with residualizing ((111)In-labeled) or nonresidualizing ((125)I-labeled) radioisotopes. Significant amounts of antibody of both affinities were degraded by tumors in vivo. Furthermore, moderate- to high-affinity mAbs targeting the same HER2 epitope with monovalent affinity above 23 nmol/L had equal tumor accumulation of residualizing radiolabel over 120 hours. Results indicated equal tumor exposure, suggesting that mAb penetration and retention in tumors reflected affinity-based differences in tumor catabolism. Together, these results suggest that high-density, rapidly internalizing antigens subject high-affinity antibodies to greater internalization and degradation, thereby limiting their penetration of tumors. In contrast, lower-affinity antibodies penetrate tumors more effectively when rates of antibody-antigen dissociation are higher than those of antigen internalization. Together, our findings offer insights into how to optimize the ability of therapeutic antibodies to penetrate tumors.

Role of ADCC in the in vivo antitumor effects of zalutumumab, a human anti-EGF receptor antibody.

e13102 Background: Zalutumumab (HuMax-EGFr, clone-2F8), a fully human IgG1 EGFR antibody, currently in phase III clinical trials, was previously demonstrated to have a dual mechanism of action. First, it blocks EGFR signaling by preventing ligand binding and inducing receptor downmodulation. This mechanism was found to be effective in established xenograft tumors at doses giving full receptor occupancy. Second, we observed in vitro induction of antibody-dependent cell-mediated cytotoxicity (ADCC), which was found to be already maximally active at very low, sub-saturating antibody concentrations. Because the contribution of ADCC to the antitumor effects of therapeutic cancer antibodies in solid tumors remains unclear we studied the importance of ADCC induction by zalutumumab in xenograft models. Methods: We prepared human EGFR antibodies with different functionalities for comparison with zalutumumab to: 1) clone 2F8-N297Q a mutant of zalutumumab, which has a nonfunctional Fc part regarding interaction with Fc receptors, 2) clone-018, a non-blocking human EGFR mAb, for which we observed ADCC in vitro as only mechanism of action and 3) clone-018-N297Q which displayed no in vitro activity. Results: Therapeutic treatment of established A431 tumor xenografts with these antibodies showed efficacy for zalutumumab and clone 2F8-N297Q only, indicating that blocking of signaling is crucial in this condition. In contrast, when given on the day of tumor induction, both zalutumumab and clone-018, but not clone-018-N297Q, were effective in preventing A431 tumor xenografts. In an experimental xenograft model, zalutumumab and clone 018 could completely prevent outgrowth of lung metastases, even when given at a low, nonsaturating dosing. Conclusions: Our experiments indicate that blocking of EGFR signaling is required for effectiveness of zalutumumab in established tumors, requiring doses giving full receptor occupancy. We conclude that induction of ADCC represents an additional, independent mechanism, which seems insufficient for reducing primary solid tumors, but is likely to have an important contribution in preventing metastases. Author Disclosure Employment or Leadership Position Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Genmab Genmab Genmab

Recent Advances Relating to the Clinical Application of Naked Monoclonal Antibodies in Solid Tumors

This review focuses on the recent advances in clinical data regarding antibody-based therapy in the management of solid tumors. We also discuss perspectives on antibody-based therapy in the future. Thorough understanding of the complex interactions between components of the immunological response has led to interest in the concept of immune-mediated therapy for solid tumors. Over the last few years, several humanized and chimeric monoclonal antibodies (MAbs) targeting human epidermal receptor 2 (HER2), epidermal growth factor receptor (EGFR), and vascular endothelial growth factor (VEGF) have been employed in treating solid tumors, including breast, colorectal, lung, head and neck, and gynecologic cancers. Trastuzumab, bevacizumab, cetuximab, and panitumumab are MAbs that are most widely used in clinical practice with acceptable rates of adverse events. Combination of MAbs with small-molecule inhibitors of the same pathway could potentially increase the efficacy and specificity of antibody-based treatment. Immune-mediated effects may be further exploited with the use of bivalent molecules.