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Purpose: Eganelisib (IPI-549) is a first-in-class, orally administered, highly selective PI3Kγ inhibitor with antitumor activity alone and in combination with programmed cell death protein 1/ligand 1 (PD-1/PD-L1) inhibitors in preclinical studies. This phase 1/1b first-in-human, MAcrophage Reprogramming in Immuno-Oncology-1 (NCT02637531) study evaluated the safety and tolerability of once-daily eganelisib as monotherapy and in combination with nivolumab in patients with solid tumors. Patients and Methods: Dose-escalation cohorts received eganelisib 10–60 mg as monotherapy (n = 39) and 20–40 mg when combined with nivolumab (n = 180). Primary endpoints included incidence of dose-limiting toxicities (DLT) and adverse events (AE). Results: The most common treatment-related grade ≥3 toxicities with monotherapy were increased alanine aminotransferase (ALT; 18%), aspartate aminotransferase (AST; 18%), and alkaline phosphatase (5%). No DLTs occurred in the first 28 days; however, toxicities meeting DLT criteria (mostly grade 3 reversible hepatic enzyme elevations) occurred with eganelisib 60 mg in later treatment cycles. In combination, the most common treatment-related grade ≥3 toxicities were increased AST (13%) and increased ALT and rash (10%). Treatment-related serious AEs occurred in 5% of monotherapy patients (grade 4 bilirubin and hepatic enzyme increases in one patient each) and 13% in combination (pyrexia, rash, cytokine release syndrome, and infusion-related reaction in ≥2 patients each). Antitumor activity was observed in combination, including patients who had progressed on PD-1/PD-L1 inhibitors. Conclusions: On the basis of the observed safety profile, eganelisib doses of 30 and 40 mg once daily in combination with PD-1/PD-L1 inhibitors were chosen for phase 2 study.

Study IPI-549-01 progression-free survival censoring rules for efficacy analyses

Purpose:Eganelisib (IPI-549) is a first-in-class, orally administered, highly selective PI3Kγ inhibitor with antitumor activity alone and in combination with programmed cell death protein 1/ligand 1 (PD-1/PD-L1) inhibitors in preclinical studies. This phase 1/1b first-in-human, MAcrophage Reprogramming in Immuno-Oncology-1 (NCT02637531) study evaluated the safety and tolerability of once-daily eganelisib as monotherapy and in combination with nivolumab in patients with solid tumors.Patients and Methods:Dose-escalation cohorts received eganelisib 10–60 mg as monotherapy (n = 39) and 20–40 mg when combined with nivolumab (n = 180). Primary endpoints included incidence of dose-limiting toxicities (DLT) and adverse events (AE).Results:The most common treatment-related grade ≥3 toxicities with monotherapy were increased alanine aminotransferase (ALT; 18%), aspartate aminotransferase (AST; 18%), and alkaline phosphatase (5%). No DLTs occurred in the first 28 days; however, toxicities meeting DLT criteria (mostly grade 3 reversible hepatic enzyme elevations) occurred with eganelisib 60 mg in later treatment cycles. In combination, the most common treatment-related grade ≥3 toxicities were increased AST (13%) and increased ALT and rash (10%). Treatment-related serious AEs occurred in 5% of monotherapy patients (grade 4 bilirubin and hepatic enzyme increases in one patient each) and 13% in combination (pyrexia, rash, cytokine release syndrome, and infusion-related reaction in ≥2 patients each). Antitumor activity was observed in combination, including patients who had progressed on PD-1/PD-L1 inhibitors.Conclusions:On the basis of the observed safety profile, eganelisib doses of 30 and 40 mg once daily in combination with PD-1/PD-L1 inhibitors were chosen for phase 2 study.

Study IPI-549-01 full protocol inclusion and exclusion criteria

Representativeness of Study Participants

Study IPI-549-01 methodology and criteria for assessing MDSCs

Background: Datopotamab deruxtecan (Dato-DXd) is an antibody-drug conjugate consisting of a humanized anti-TROP2 IgG1 monoclonal antibody conjugated to a potent topoisomerase I inhibitor payload via a stable tetrapeptide-based cleavable linker. Preliminary results from the phase 1 TROPION-PanTumor01 study demonstrate that Dato-DXd has encouraging antitumor activity and a manageable safety profile in patients with non-small cell lung cancer (NSCLC) (Meric-Bernstam, ASCO 2021) and those with triple-negative breast cancer (TNBC) (Bardia, ESMO BC 2021). Updated results from the TNBC cohort are presented here. Methods: TROPION-PanTumor01 (NCT03401385) is a phase 1, multi-center, open-label, 2-part study evaluating Dato-DXd in previously treated patients with solid tumors. Based on the dose-escalation results in patients with NSCLC, Dato-DXd 6 mg/kg intravenously every 3 weeks is being evaluated in patients with advanced/metastatic TNBC and HR+/HER2− breast cancer who relapsed/progressed on standard therapies. Two patients with TNBC received Dato-DXd 8 mg/kg prior to selection of 6 mg/kg for dose expansion. Safety and efficacy were assessed, including objective response rate (ORR) per RECIST version 1.1 by blinded independent central review (BICR). Results: As of the April 6, 2021, data cutoff, 43 patients with TNBC had received ≥1 dose of Dato-DXd, with 27 patients (63%) continuing and 16 patients (37%) discontinuing treatment all due to disease progression. The median age was 53 years (range, 32-82 years). Forty-one patients (95%) had received ≥2 prior lines of therapy; 19 patients (44%) had received prior immunotherapy and 7 (16%) had received prior sacituzumab govitecan. The median duration of treatment was 2.8 months (range, 0.7-6.9 months). The median follow-up was 3.9 months (range, 0.3-9.2 months). Among 38 patients evaluable for response, the ORR by BICR was 39% (15 partial responses [PR]), with 12 confirmed and 3 pending confirmation. The disease control rate was 84% (32/38). The median time to response was 1.35 months (1.2-3.2 months) for the 12 confirmed PRs. All-cause treatment-emergent adverse events (TEAEs; any grade, grade ≥3) were observed in 95% and 35% of patients, respectively; 2 events were grade 4 and 0 grade 5. The most common TEAEs (any grade [≥30%], grade ≥3) included nausea (58%, 0%), stomatitis (53%, 9%), alopecia (35%, N/A), vomiting (35%, 2%), and fatigue (33%, 7%). One patient had grade 3 decreased neutrophil count; no cases of grade ≥3 diarrhea were observed. No cases of treatment-related interstitial lung disease as adjudicated by an independent committee were reported. Serious TEAEs were observed in 5 patients (12%); no TEAEs were associated with death. Dose reductions occurred in 9 patients due to stomatitis, fatigue, mucosal inflammation, dry eye, retinal exudates, and blurred vision (multiple counts per TEAE). Three patients had dose interruptions due to stomatitis, mucosal inflammation, bronchitis, and musculoskeletal chest pain. No patients discontinued treatment due to adverse events. Conclusions: Preliminary results showed that Dato-DXd demonstrates promising antitumor activity with a manageable safety profile in patients with previously treated advanced/metastatic TNBC; confirmatory studies in patients with breast cancer are warranted. Citation Format: Ian Krop, Dejan Juric, Toshio Shimizu, Anthony Tolcher, Alexander Spira, Toru Mukohara, Aaron E. Lisberg, Takahiro Kogawa, Kyriakos P. Papadopoulos, Erika Hamilton, Senthil Damodaran, Jonathan Greenberg, Wen Gu, Fumiaki Kobayashi, Ferdinand Guevara, Takahiro Jikoh, Yui Kawasaki, Funda Meric-Bernstam, Aditya Bardia. Datopotamab deruxtecan in advanced/metastatic HER2- breast cancer: Results from the phase 1 TROPION-PanTumor01 study [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr GS1-05.

Supplementary Table S1 shows inclusion and exclusion criteria for each treatment arm that enrolled patients

Supplementary Table S1 - PDF file 52K, Best overall tumor response (RECIST)

Supplementary Figure S1 shows the study design.

Purpose: The vascular disrupting agent ombrabulin rapidly reduces tumor blood flow and causes necrosis in vivo. A phase I dose-escalation study was designed to determine the recommended phase II dose (RP2D) of single-agent ombrabulin administered once every three weeks in patients with advanced solid malignancies.Experimental Design: Ombrabulin (30-minute infusion) was escalated from 6 to 60 mg/m2, with RP2D cohort expansion. Safety, tumor response, pharmacokinetics, and pharmacodynamic biomarkers were evaluated.Results: Eleven dose levels were evaluated in 105 patients. Two patients had dose-limiting toxicities in cycle 1 during escalation: grade 3 abdominal pain at 50 mg/m2, grade 3 tumor pain/grade 3 hypertension at 60 mg/m2, and the RP2D was 50 mg/m2 (39 patients). Common toxicities were headache, asthenia, abdominal pain, nausea, diarrhea, transient hypertension, anemia, and lymphopenia. No clinically significant QTc prolongations or left ventricular ejection fraction (LVEF) decreases occurred. Ombrabulin was rapidly converted to its active metabolite RPR258063 (half-life 17 minutes and 8.7 hours, respectively), both having dose-proportional exposure. Weak inhibition of CYP2C19-mediated metabolism occurred at the clinical doses used and there was no effect on CYP1A2 and CYP3A4. A patient with rectal cancer had a partial response and eight patients had stable disease lasting four months or more. Circulating endothelial cells (CEC), VEGF, and matrix metalloproteinase (MMP)-9 levels increased significantly six to 10 hours postinfusion in a subset of patients.Conclusions: The recommended schedule for single-agent ombrabulin is 50 mg/m2 every 3 weeks. CECs, VEGF, and MMP-9 are potential biomarkers of ombrabulin activity. Clin Cancer Res; 19(17); 4832–42. ©2013 AACR.

Supplementary Figure Legends - PDF file 62K, Supplementary Figure legends

Supplementary Fig. S2 - PDF file 123K, Change in Fridericia-corrected QT interval from baseline vs ombrabulin (A) and RPR258063 (B) concentrations as the predictor

Supplementary Text - PDF file 76K, DCE methodology and results

Background: Hypersialylation (excessive sialoglycans) on tumor cells has been known to be associated with poorer cancer outcomes for more than 40 years. Sialoglycans are immune suppressive and promote tumor immune evasion by binding to sialoglycan receptors (e.g. Siglecs) expressed on immune cells. However, redundant immune cell expression among Siglecs has posed a challenge for receptor-targeting therapeutic approaches. E-602 is a first-in-class fusion protein of engineered human sialidase (Neu2) and a human IgG1 Fc region. The dimeric sialidase moieties of E-602 circumvent the redundancy of this biology by directly cleaving terminal sialic acid residues from sialoglycans on immune and tumor cells. In preclinical studies, E-602 enhanced immune function by augmenting antigen-specific priming and activation of T cells and restoring function of exhausted-like T cells, and E-602 demonstrated antitumor activity as monotherapy in multiple mouse tumor models. Methods: A Phase 1/2 first-in-human dose escalation study is evaluating the safety, pharmacokinetics (PK), pharmacodynamics (PD), and antitumor activity of E-602 in patients with advanced cancers. Eligible patients with select advanced solid tumors were treated with E-602 IV once weekly at dose levels between 1 and 30 mg/kg. Circulating immune cells were analyzed for changes in sialylation and immunophenotyping by flow cytometry. Changes in circulating cytokines were measured by immunoassays. Results: As of January 6, 2023, 32 patients were treated with at least one dose of E-602. The most common tumors treated were colorectal (n=18) and pancreatic (n=6). Doses up to 30 mg/kg were tolerated with no dose-limiting toxicities. The most frequent adverse event was infusion-related reactions which were primarily grade 1-2 and clinically manageable. PK was linear across the evaluated dose range with an estimated T1/2 of 9-24 hours. Dose dependent PD observations included (1) desialylation of peripheral CD8+ T, CD4+ T, and NK cells, remaining detectable in some patients at 7 days post-dose; (2) increases in the immune activation marker, CD69, on peripheral CD8+ T, CD4+ T, and NK cells; and (3) increases in the IFNγ-dependent chemokine CXCL10, TNF-α, and MIP1-β. Thus far, response-evaluable patients have had stable or progressive disease. Additional safety, PK, PD, and clinical outcomes for other patients treated as part of backfill at multiple dose levels will be reported at the meeting. Conclusion: E-602 is tolerated at doses up to 30 mg/kg. Consistent with preclinical findings, dose-dependent desialylation and immune system activation were observed. Based on the observed tolerability and PD effects, the Phase 2 portion of the study to evaluate clinical activity of E-602 monotherapy in patients with checkpoint-inhibitor resistant NSCLC and melanoma will proceed. Citation Format: Jason J. Luke, Melissa Johnson, Anthony Tolcher, Christopher T. Chen, Tong Dai, Brendan D. Curti, Anthony El-Khoueiry, Mario Sznol, Brian S. Henick, Christine Horak, Pushpa Jayaraman, Christopher B. Cole, Dawn Wilson, Lizhi Cao, Li Peng, David Feltquate, Deanne Lathers, Manish R. Sharma. GLIMMER-01: initial results from a phase 1 dose escalation trial of a first-in-class bi-sialidase (E-602) in solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT034.

Background: ELU001 is a novel, first-in-class, new molecular entity described as a C’Dot Drug Conjugate (CDC). ELU001 consists of ~13 folic acid targeting moieties and a payload of ~22 molecules of the topoisomerase-1 inhibitor, exatecan. Folic acid and exatecan are covalently bound by non-cleavable and cathepsin-B cleavable linkers, respectively, to short polyethylene glycol chains which surround the C’Dot’s silica core. CDCs are very small (~6 nm), allowing greater ability to penetrate more efficiently into solid tumors compared to ADCs. CDCs are rapidly eliminated by the kidneys, which is expected to lead to less toxicity than ADCs that have a longer half-life in circulation. ELU001’s high avidity is designed to promote binding to FRα on the surface on FRα overexpressing cancer cells with a wide range of antigen expression including high, moderate and low expressing tumor cells. Following antigen binding, ELU001 internalizes into the tumor cell, and traffics to the lysosome where enzymatic cleavage releases the exatecan payload. The first-in-human trial, ELU-FRα-1, is currently recruiting patients that have advanced, recurrent or refractory tumors associated with indications that are known to potentially overexpress FRα and have been shown to be topoisomerase 1 inhibitor-sensitive, and, in the opinion of the Investigator, have no satisfactory therapeutic options available. Methods: This is a Phase 1/2 multicenter, open label clinical trial with two parts: Part 1 Dose Escalation and Part 2 Tumor Group Expansion Cohort(s). Part 1 is a basket trial enrolling patients with cancer types with a high likelihood of having FRα overexpressing tumors, (specifically, ovarian, endometrial, colorectal, gastric, gastroesophageal junction, triple negative breast, or non-small cell lung cancers, or cholangiocarcinoma). Patients are receiving ELU001 weekly (QW) (once a week for 3 weeks, 1 week rest), every other week (Q2W, with no rest between cycles), or every three weeks (Q3W). Analysis of FRα expression will be retrospectively determined. Part 2 will use Simon’s Two-Stage design to evaluate 4-6 Expansion Cohorts, comprised of tumor histologies anticipated to have greatest activity to ELU001 treatment. FRα will be prospectively determined. The primary objective for Part 1 is to identify the MTD/RP2D. The primary objective for Part 2 is to determine the ORR. Secondary objectives include DOR, PFS, TFST, PFS2, OS, frequency, severity and tolerability of adverse events, PK, ADA, and FRα expression assessments. Part 1 Dose Escalation will recruit about 25 patients per dose regimen (QW; Q2W; Q3W). The first stage of Part 2 (Dose Expansion) will recruit about 15 patients per tumor group expansion cohort. The study is actively enrolling in the US and currently recruiting in Q2W Cohort 201 and Q3W Cohort A. QW Cohorts 1-3 and Q2W Cohort 101 are complete. Clinical trial information: NCT05001282. Citation Format: Wen Wee Ma, Anthony Tolcher, Cesar A. Perez, Douglass Orr, Erika Hamilton, Yujie Zhao, Yonina Murciano-Goroff, Carey Anders, Gregory P. Adams, Catherine W. Reddick, Eliel Bayever. ELU-FRα-1: a study to evaluate ELU001 in patients with solid tumors that overexpress folate receptor alpha (FRα) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT255.

BackgroundAvailability of checkpoint inhibitors has created a paradigm shift in the management of patients with solid tumors. Despite this, most patients do not respond to immunotherapy, and there is considerable interest in developing combination therapies to improve response rates and outcomes. B7-H3 (CD276) is a member of the B7 family of cell surface molecules and provides an alternative immune checkpoint molecule to therapeutically target alone or in combination with programmed cell death-1 (PD-1)–targeted therapies. Enoblituzumab, an investigational anti-B7-H3 humanized monoclonal antibody, incorporates an immunoglobulin G1 fragment crystallizable (Fc) domain that enhances Fcγ receptor-mediated antibody-dependent cellular cytotoxicity. Coordinated engagement of innate and adaptive immunity by targeting distinct members of the B7 family (B7-H3 and PD-1) is hypothesized to provide greater antitumor activity than either agent alone.MethodsIn this phase I/II study, patients received intravenous enoblituzumab (3–15 mg/kg) weekly plus intravenous pembrolizumab (2 mg/kg) every 3 weeks during dose-escalation and cohort expansion. Expansion cohorts included non–small cell lung cancer (NSCLC; checkpoint inhibitor [CPI]–naïve and post-CPI, programmed death-ligand 1 [PD-L1] ResultsOverall, 133 patients were enrolled and received ≥1 dose of study treatment. The maximum tolerated dose of enoblituzumab with pembrolizumab at 2 mg/kg was not reached. Intravenous enoblituzumab (15 mg/kg) every 3 weeks plus pembrolizumab (2 mg/kg) every 3 weeks was recommended for phase II evaluation. Treatment-related adverse events occurred in 116 patients (87.2%) and were grade ≥3 in 28.6%. One treatment-related death occurred (pneumonitis). Objective responses occurred in 6 of 18 (33.3% [95% CI 13.3 to 59.0]) patients with CPI-naïve HNSCC and in 5 of 14 (35.7% [95% CI 12.8 to 64.9]) patients with CPI-naïve NSCLC.ConclusionsCheckpoint targeting with enoblituzumab and pembrolizumab demonstrated acceptable safety and antitumor activity in patients with CPI-naïve HNSCC and NSCLC.Trial registration numberNCT02475213.

Background: XB002 is an antibody drug conjugate (ADC), with a high affinity human mAb directed against tissue factor (TF) conjugated to a novel cytotoxic agent (payload), ZLA (Zymelink Auristatin). TF is a protein overexpressed in many solid tumors and is associated with disease progression and poor prognosis. XB002 binds to TF without interfering with the coagulation pathway. With its mechanism of action, XB002 has been designed to improve the therapeutic potential of ADCs targeting TF and has demonstrated activity in several solid tumor xenograft models. The purpose of this ongoing first-in-human study is to evaluate the safety, tolerability, pharmacokinetics (PK), immunogenicity (anti-drug antibodies) and preliminary antitumor activity of XB002. Presented here is the trial design. Methods: This is a phase 1, non-randomized, open-label, multicenter, dose-escalation and dose expansion study (NCT04925284). Patients must be ≥18 years old and have an ECOG performance status of 0-1 and adequate organ and marrow function. Patients will be treated until radiographic progression per Response Evaluation Criteria in Solid Tumors (RECIST v1.1) or unacceptable toxicity. The dose-escalation stage will use a modified i3+3 design; patients with advanced solid tumors (~21 patients) will receive XB002 IV once every 3 weeks. The primary endpoint for dose escalation is the maximum tolerated dose (MTD)/recommended dose (RD) of XB002 per Cohort Review Committee. The MTD/RD will be further evaluated in multiple tumor-specific expansion cohorts of advanced solid tumors (~30 patients per cohort) using a Simon’s 2-stage design. Tumor-specific cohorts (number of prior lines of systemic therapy for advanced disease) include: non-small cell lung cancer (≤3); urothelial cancer (≤3); platinum-resistant epithelial ovarian cancer (≤3); cervical cancer (≤2); squamous cell carcinoma of head and neck (≤3); and pancreatic cancer (1-2). Patients must have measurable disease per RECIST v1.1 and had radiographic progression during or after their last systemic therapy. The primary endpoint for cohort expansion is objective response rate per RECIST v1.1 by investigator. Additional endpoints include safety/tolerability, XB002 pharmacokinetics and immunogenicity, duration of response and PFS per RECIST v1.1 by investigator, overall survival, and changes in tumor markers from baseline. Citation Format: Melissa Johnson, Susanna Ulahannan, Andrae Vandross, Haeseong Park, Leo Faoro, Raffaella Faggioni, Jing Li, Yu-Lin Chang, Shailaja Uttamsingh, Anthony Tolcher. A first-in-human phase 1 study of the safety and pharmacokinetics of XB002 in patients with inoperable locally advanced or metastatic solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT254.

Background Tumor-targeted drug delivery technologies are urgently needed to overcome the lack of tumor selectivity, a major drawback of conventional chemotherapy. In addition, the acidic intercellular microenvironment in solid tumors traps weak acid/base chemotherapy agents, preventing necessary intracellular concentrations in tumour cells. An alphalex conjugate, which contains a low-pH insertion peptide, a linker, and a payload, is designed to overcome these limitations. Unlike antibody drug conjugates, these peptide drug conjugates target tumors in an antigen-agnostic manner. At pH ≥7.0, the peptide is unstructured. In the low-pH tumor microenvironment, the peptide forms an alpha helix, inserts directionally in the cell membrane delivering the linker and payload intracellularly where the linker is cleaved. CBX-12 consists of the pH-sensitive peptide, a self-immolating linker, and the topoisomerase 1 (TOP1) inhibitor exatecan. Methods CBX-12-101 is a first-in-human, open-label, dose-escalation, safety, pharmacokinetics (PK), and biomarker study of CBX-12 in patients with advanced or metastatic refractory solid tumors. CBX-12 is administered as a 1-hour intravenous infusion. Two dosing schedules, daily x 5 every 3 weeks (Part A) and daily x 3 every 3 weeks (Part B), are being evaluated. The starting dose in Part A is 0.25 mg/kg. Single-patient cohorts will be enrolled initially, with dose-escalations up to 100% of the prior dose, until a patient has a ≥ Grade 2 adverse event (AE) considered possibly related to CBX-12 during Cycle 1 (the DLT period), at which time 2 additional patients will be enrolled in that cohort, and a 3 + 3 design will subsequently be utilized. Further dose escalations may be no more than 50% of the prior dose. After at least 2 cohorts have been evaluated in Part A, Part B will open for accrual. Maximum tolerated doses and recommended phase 2 doses will be determined for each dosing schedule. The PK of the CBX-12 conjugate and free exatecan will be determined. The stability of the conjugate in circulation will be evaluated by the ratio of CBX-12 to free exatecan. Pre- and on-treatment tumor biopsies are required. Biomarker and pharmacodynamic evaluations including measuring intratumor exatecan levels, TOP1, gamma H2AX and schlafen-11 are planned. Antitumor activity will be assessed per RECIST v 1.1. Phase 2 expansion cohorts are planned in patients with platinum-resistant ovarian and small cell lung cancer. As of July 2021, patients are enrolling in Part A Cohort 2 at a dose of 0.50 mg/kg. Citation Format: Anthony Tolcher, Joseph Paul Eder, David Sommerhalder, Sophia Gayle, Paul Pearson, Deb Chapman, Arthur P. DeCillis, Anish Thomas, Funda Meric-Bernstam. A phase 1/2 trial of CBX-12, an alphalexTM peptide drug conjugate, in patients with advanced or metastatic refractory solid tumors [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P047.

BackgroundT cell immunoreceptor with immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domains (TIGIT) is an inhibitory receptor expressed on T cells, including regulatory T cells (Tregs) and natural killer (NK) cells. In the tumor microenvironment, TIGIT is often overexpressed and directly inhibits both T cell and NK cell effector function and proliferation. TIGIT is also involved in regulating Treg function. Therefore, inhibiting the TIGIT-related immunosuppressive pathway may result in antitumor activity. M6223 is an intravenously (IV) administered, human, antagonistic, immunoglobulin G1 (IgG1) anti-TIGIT antibody with an Fc mediated effector region. Bintrafusp alfa is a first-in-class bifunctional fusion protein composed of the extracellular domain of the human transforming growth factor β receptor II (a TGFβ ”trap”) fused to a human IgG1 monoclonal antibody blocking programed death ligand 1 (PD-L1). As TIGIT and programed death receptor 1 (PD-1) are co-expressed on T cells, dual inhibition of both immune checkpoints may enhance antitumor activity. This phase Ia study (NCT04457778) aims to determine the safety, tolerability, maximum tolerated dose and recommended dose for expansion of M6223 monotherapy and M6223 (both the once every 2 weeks [Q2W] and once every 3 weeks [Q3W] regimens) in combination with bintrafusp alfa. Secondary objectives include the evaluation of pharmacokinetics and clinical activity of M6223 with and without bintrafusp alfa.MethodsEligible patients include those aged ≥18 years with: an Eastern Cooperative Oncology Group performance status ≤1; adequate baseline hematological, renal and hepatic function; and histologically or cytologically proven locally advanced or advanced solid tumors, for which no effective standard therapy is available. Patients previously treated with a TIGIT targeting agent or bintrafusp alfa are excluded. Patients with brain metastases are also excluded, except those without neurological symptoms ≥4 weeks before start of treatment and those receiving either a stable or decreasing dose of steroids AcknowledgementsThe authors would like to thank Daniel Holland of the healthcare business of Merck KGaA, Darmstadt, Germany for his involvement and contribution to the design and conduct of this study. Medical writing assistance was provided by David Lester of Bioscript Stirling Ltd, Macclesfield, UK, and funded by the healthcare business of Merck KGaA, Darmstadt, Germany [CrossRef Funder ID: 10.13039/100009945].Funding: The healthcare business of Merck KGaA, Darmstadt, Germany (CrossRef Funder ID: 10.13039/100009945).Trial RegistrationNCT04457778Ethics ApprovalThe study and the protocol were approved by the Institutional Review Board or ethics committee at each site. All patients provided written informed consent before any study procedures were performed.

The differential sensitivity of some tumors to paclitaxel and docetaxel raises questions regarding the specific mechanisms responsible for the discrepant sensitivity to these taxanes.Docetaxel and paclitaxel were evaluated and compared at maximum tolerated doses (MTD) and 0.5 MTDs against the human pediatric tumor xenograft models SK-N-MC and IMR32 (neuroblastoma), RH1 and RH30 (rhabdomyosarcoma) and KHOS/NP (osteosarcoma), with 8-10 animals per group. The drug effects on the expression of the beta-tubulin isotypes, Bcl-2, Bax, Bcl-XL and proteomic profiles were evaluated by immunobloting and SELDI mass spectrometry in tumor xenografts dosed at 0.5 MTDs.At MTDs, docetaxel was superior in neuroblastoma and osteosarcoma, while paclitaxel was more active in the rhabdomyosarcoma models. Docetaxel showed remarkable efficacy in KHOS/NP even at 0.5 MTD. The drugs had significantly different, yet highly heterogeneous effects on the tumor levels of betaI-tubulin (RH30), betaIII-tubulin (IMR32, KHOS/NP, RH]), Bax (IMR32, SK-N-MC) and Bcl-XL (KHOS/NP). In contrast, six protein species identified by proteomic profiling were consistently and differentially regulated by docetaxel and paclitaxel in all KHOS/NP xenografts.Anticancer activity showed no apparent correlation with drug effects on beta-tubulin isotypes and apoptotic markers. The mass spectrometry approach has potential for the discovery of proteomic biomarkers for drug sensitivity.