A Phase I, Open-Label, Dose-Escalation Study of the OX40 Agonist Ivuxolimab in Patients with Locally Advanced or Metastatic Cancers

PURPOSE

Stimulation of effector T cells is an appealing immunotherapeutic approach in oncology. OX40 (CD134) is a costimulatory receptor expressed on activated CD4⁺ and CD8⁺ T cells. Induction of OX40 following antigen recognition results in enhanced T-cell activation, proliferation, and survival, and OX40 targeting shows therapeutic efficacy in preclinical studies. We report the monotherapy dose-escalation portion of a multicenter, phase I trial (NCT02315066) of ivuxolimab (PF-04518600), a fully human immunoglobulin G2 agonistic monoclonal antibody specific for human OX40.

PATIENTS AND METHODS

Adult patients (N = 52) with selected locally advanced or metastatic cancers received ivuxolimab 0.01 to 10 mg/kg. Primary endpoints were safety and tolerability. Secondary/exploratory endpoints included preliminary assessment of antitumor activity and biomarker analyses.

RESULTS

The most common all-causality adverse events were fatigue (46.2%), nausea (28.8%), and decreased appetite (25.0%). Of 31 treatment-related adverse events, 30 (96.8%) were grade ≤2. No dose-limiting toxicities occurred. Ivuxolimab exposure increased in a dose-proportionate manner from 0.3 to 10 mg/kg. Full peripheral blood target engagement occurred at ≥0.3 mg/kg. Three (5.8%) patients achieved a partial response, and disease control was achieved in 56% of patients. Increased CD4⁺ central memory T-cell proliferation and activation, and clonal expansion of CD4⁺ and CD8⁺ T cells in peripheral blood were observed at 0.1 to 3.0 mg/kg. Increased immune cell infiltrate and OX40 expression were evident in on-treatment tumor biopsies.

CONCLUSIONS

Ivuxolimab was generally well tolerated with on-target immune activation at clinically relevant doses, showed preliminary antitumor activity, and may serve as a partner for combination studies.

523 Preliminary clinical experience with XmAb20717, a PD-1 x CTLA-4 bispecific antibody, in patients with advanced solid tumors

Background

XmAb20717 is a humanized bispecific monoclonal antibody that simultaneously targets PD-1 and CTLA-4. We report updated data on patients treated at the recommended expansion dose from an ongoing, multicenter, Phase 1, dose-escalation and -expansion study of intravenous XmAb20717 in patients with selected advanced solid tumors that progressed after treatment with all standard therapies or with no standard therapeutic options.

Methods

A maximum tolerated dose was not reached in dose escalation. XmAb20717 10 mg/kg every 2 weeks (Q2W) was selected as the expansion dose, based on consistent T-cell proliferation in peripheral blood indicative of dual PD-1/CTLA-4 checkpoint blockade, and response to treatment (RECIST[1.1]).1 Parallel expansion cohorts included ~20 patients each with melanoma, renal cell carcinoma (RCC), non-small cell lung cancer (NSCLC), castration-resistant prostate cancer (CRPC), and a basket of tumor types without an FDA-approved checkpoint inhibitor (CI). Patients treated with 10 mg/kg in dose escalation were pooled with expansion cohorts for analysis of clinical activity and safety.

Results

As of 9 June 2021, 110 patients, ranging in age from 39 to 89 years and 66.4% male, were treated, and 5 were continuing treatment. Patients had received a median of 4 prior systemic treatment regimens, including CI therapy for 64.5%. The objective response rate was 13.0% (10/77 patients evaluable for efficacy), including 1 complete response (melanoma [confirmed]) and 9 partial responses (confirmed: 1 melanoma, 2 RCC, 2 CRPC, 1 ovarian cancer; unconfirmed: 1 melanoma, 2 NSCLC). The CRPC responders (2/7 with RECIST-measurable disease) had confirmed PSA decreases ≥ 50% from baseline (to 0.02 and 0.3 ng/mL); neither had progression on bone scans. All responders had prior CI exposure, except those with CRPC. Robust CD4 and CD8 T-cell activation was seen. Low baseline tumoral expression of myeloid recruitment genes, including IL-8, was associated with clinical benefit. Grade ≥ 3 immunotherapy-related adverse events in ≥ 3 patients included rash (16.4%), transaminase elevations (9.1%), hyperglycemia (4.5%), acute kidney injury (3.6%), amylase and lipase increased (2.7%), and lipase increased (2.7%).

Conclusions

Preliminary data indicate 10 mg/kg XmAb20717 Q2W was associated with complete and partial responses in multiple tumor types and was generally well-tolerated in these heavily pretreated patients with advanced cancer. Changes in T-cell populations in the periphery and tumor are consistent with robust dual checkpoint blockade. These findings support further development of XmAb20717 in advanced solid tumors, including metastatic prostate cancer.

Trial Registration

NCT03517488

References

Shum E, Daud A, Reilley M, et al. Preliminary safety, pharmacokinetics/pharmacodynamics, and antitumor activity of XmAb20717, a PD-1 x CTLA-4 bispecific antibody, in patients with advanced solid tumors. JITC 2020;8(3):A247-8.

Ethics Approval

The study was approved by each institution’s IRB.

407 Preliminary safety, pharmacokinetics/pharmacodynamics, and antitumor activity of XmAb20717, a PD-1 x CTLA-4 bispecific antibody, in patients with advanced solid tumors

Background

XmAb20717 is a humanized bispecific monoclonal antibody that simultaneously targets PD-1 and CTLA-4. We report preliminary data from an ongoing, multicenter, Phase 1 study investigating the safety/tolerability, pharmacokinetics/pharmacodynamics, and clinical activity (RECIST 1.1) of XmAb20717 in patients with selected advanced solid tumors.

Methods

A 3+3 dose-escalation design was used to establish a maximum tolerated (MTD)/recommended dose for evaluation in parallel expansion cohorts, including melanoma, renal cell carcinoma, non-small cell lung cancer (NSCLC), prostate cancer, and a basket of tumor types without an FDA-approved checkpoint inhibitor (CI; n≤20 each). XmAb20717 was administered as an infusion on Days 1 and 15 of each 28-day cycle.

Results

As of 08Jul2020, 109 patients had been treated (table 1), and 30 were continuing treatment. In escalation, 6 dose levels (0.15–10.0 mg/kg) were evaluated (n=34); an MTD was not established. Expansion cohorts were initiated at 10 mg/kg (n=72), and a 15 mg/kg escalation cohort was added (n=3). T-cell proliferation was noted in peripheral blood at doses as low as 3 mg/kg and was highest at 10 mg/kg. At this dose, consistent proliferation of CD8+ and CD4+ T cells was observed, indicative of dual PD-1 and CTLA-4 checkpoint blockade (figure 1). Paired pre- and post-dosing biopsies showed increased intratumoral T-cell infiltration and IFN-response signatures following treatment. Grade 3/4 treatment-related adverse events (TRAEs) reported for ≥3 patients included rash (13%), transaminase elevations (7%), lipase increased (4% [2% with amylase increased]), and acute kidney injury (3%), all considered immune-related. There were 2 Grade 5 TRAEs: immune-mediated pancreatitis (in the presence of pancreatic metastases) and immune-mediated myocarditis (Grade 4) that contributed to respiratory failure. A complete response was reported as the best overall response for 1 patient (melanoma); partial responses were reported for 5 patients (2 melanoma, 2 NSCLC, 1 ovarian). The objective response rate was 13% overall and 21% at 10 mg/kg (6/46 and 6/29 evaluable patients, respectively). All responders had prior CI exposure. Responses were observed only at 10 mg/kg and, within the 10 mg/kg group, appeared to correlate with higher peak serum concentration and area under the curve.

Abstract 407 Table 1

Demographics and baseline characteristics

Abstract 407 Figure 1

Mean change from baseline in percentage of Ki67+ T–cell expression in peripheral blood during first two cycles of XmAb20717

Conclusions

XmAb20717 induced T-cell proliferation in peripheral blood consistent with dual-checkpoint blockade. Preliminary data indicate XmAb20717 was generally well-tolerated and associated with evidence of antitumor activity in CI-pretreated patients with various types of advanced solid tumors.

Trial Registration

NCT03517488

Ethics Approval

The study was approved by each institution’s IRB.

Abstract 3521: Transcriptome analysis of TCGA prostate cancer samples identifies an association of poorer survival and aggressive disease biology with CDC-like kinase (CLK) expression and spliceosome regulation

In prostate cancer, alternative splicing of mRNA and spliceosome activity are implicated in several areas of disease pathogenesis. This is exemplified by the strong association of androgen receptor splice variants with treatment resistance and poor clinical outcome in castration-resistant disease. Therefore, pharmacologic targeting of spliceosome-regulating proteins such as CLKs and serine/arginine-rich splicing factors (SRSFs) represents a novel treatment approach for prostate cancer. To evaluate the therapeutic potential of inhibiting CLK activity in prostate cancer, the association between splicing-related gene expression and survival was investigated in The Cancer Genome Atlas Prostate Adenocarcinoma (TCGA-PRAD) data collection (N=495). Survival analysis of RNA-seq data assessed 17,879 genes to measure their association with progression-free interval (PFI). Using transcript per million as the metric for normalized gene expression, age-adjusted Cox proportional hazards regression models were performed for each gene (R v3.6.0, coxph v2.43-3). A total of 3,145 genes significantly correlated with worse prognosis (P-adj<0.10, Cox coefficient >0). CLK1 (P-adj=0.0218, HR=1.5939), CLK2 (P-adj=0.001298, HR=2.1393), and SRSF2 (P-adj=0.00167, HR=3.2917) were found to be positively associated with poorer PFI, ranking 1202, 400, and 437, respectively. Reactome pathway analysis of the significant gene set showed that mRNA splicing and processing accounted for 5 of the 19 pathways that were strongly associated with poorer PFI. An additional pathway analysis (GSEA v.3.0, MSigDB v6.2) of tumors categorized by PTEN status to assess relationship with disease severity showed that mRNA splicing (P-adj=0.0243, NES=1.7714) was enriched in PTEN-null vs. PTEN-wt tumors. Other pathways of interest, including Wnt signaling (P-adj=0.0187, NES=1.846), cell cycle (P-adj=0.0124, NES=1.974), chromatin remodeling (P-adj=0.0135, NES=1.901), DNA damage repair (P-adj=0.013974, NES=1.8934), and PTEN regulation (P-adj=0.0230, NES=1.7861), were also enriched in PTEN-null tumors. Lastly, a survival analysis within all TCGA-PRAD patients showed that low CLK1 (P=0.03) and CLK2 (P=0.0004) expression, individually, were associated with a better prognosis vs. their high-expressing counterparts. Analysis of CLK3 and CLK4 expression did not reach statistical significance. Collectively, these findings revealed an association of spliceosome activity and CLK1/2 expression with aggressive disease biology in prostate cancer. A Phase 1 study of SM08502, a novel, small-molecule pan-CLK inhibitor, in subjects with advanced solid tumors is ongoing (NCT03355066). This analysis nominates prostate cancer as a tumor type worth further exploring for the clinical activity of SM08502.

Citation Format: Shawn Cho, Atish D. Choudhury, Catherine Fleener, Long Do, Carine Bossard, Heekyung Chung, Timothy J. Phalen, Steven Cha. Transcriptome analysis of TCGA prostate cancer samples identifies an association of poorer survival and aggressive disease biology with CDC-like kinase (CLK) expression and spliceosome regulation [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3521.

Peripheral immune-based biomarkers in cancer immunotherapy: can we realize their predictive potential?

The immunologic landscape of the host and tumor play key roles in determining how patients will benefit from immunotherapy, and a better understanding of these factors could help inform how well a tumor responds to treatment. Recent advances in immunotherapy and in our understanding of the immune system have revolutionized the treatment landscape for many advanced cancers. Notably, the use of immune checkpoint inhibitors has demonstrated durable responses in various malignancies. However, the response to such treatments is variable and currently unpredictable, the availability of predictive biomarkers is limited, and a substantial proportion of patients do not respond to immune checkpoint therapy. Identification and investigation of potential biomarkers that may predict sensitivity to immunotherapy is an area of active research. It is envisaged that a deeper understanding of immunity will aid in harnessing the full potential of immunotherapy, and allow appropriate patients to receive the most appropriate treatments. In addition to the identification of new biomarkers, the platforms and assays required to accurately and reproducibly measure biomarkers play a key role in ensuring consistency of measurement both within and between patients. In this review we discuss the current knowledge in the area of peripheral immune-based biomarkers, drawing information from the results of recent clinical studies of a number of different immunotherapy modalities in the treatment of cancer, including checkpoint inhibitors, bispecific antibodies, chimeric antigen receptor T cells, and anti-cancer vaccines. We also discuss the various technologies and approaches used in detecting and measuring circulatory biomarkers and the ongoing need for harmonization.

Abstract CT010: Pharmacodynamic (PD) changes in tumor RNA expression and the peripheral blood T cell receptor (TCR) repertoire in a phase I study of OX40 agonistic monoclonal antibody (mAb) PF-04518600 (PF-8600)

Introduction: PF-8600 is a fully human IgG2 agonistic mAb against the tumor necrosis factor superfamily receptor OX40. OX40 improves T cell survival, proliferation, and activation and may enhance anti-tumor immunity. In an ongoing phase I study (NCT02315066) of 52 patients (pts) with melanoma, hepatocellular carcinoma, head and neck carcinoma, or renal cell carcinoma treated with PF-8600 monotherapy in dose escalation, 2 pts had best overall response of partial response (PR) and 27 of stable disease. PF-8600 was well-tolerated at all doses. Peripheral blood flow cytometry had previously shown increased proliferation and activation of CD4 central memory T cells at certain dose levels, suggesting a PD effect. RNAseq analysis of tumor biopsy samples and TCR sequencing of peripheral blood were used to further support proof of mechanism.

Methods: Biopsy samples at baseline and wk 6 were collected from 5 dose cohorts [0.1 (4), 0.3 (3), 1.5 (4), 3.0 (3) and 10.0 (2), dose in mg/kg (n)]. Biopsy tissue was analyzed by RNAseq and gene ranking-based gene set enrichment analysis (FGSEA) to identify immune pathways potentially up-regulated by OX40. CD4/CD8 cells were isolated from peripheral blood samples from 4 dose cohorts (0.1, 0.3, 1.5, and 3.0 mg/kg). DNA was extracted for sequencing of the TCR-β chain complementarity-determining region 3 (CDR3).

Results: In a combined analysis of samples from pts dosed with ≥1.5 mg/kg, the top 3 gene sets showing enrichment at wk 6 of therapy were associated with inflammatory response, interferon-γ response and allograft rejection. These gene sets were identical to the top 3 most enriched in tumor from a syngeneic mouse tumor model exposed to a murine OX40 agonist. This pattern of enrichment was not observed if samples from lower doses were included in the analysis. TCR sequencing revealed clonal expansion of CD4/CD8 T cells at all dose levels at wk 6 [CD4: mean = 8 expanded clones per 100,000 clones (range = 1 - 80), CD8: mean = 56 (range = 1 - 500)]. The 2 patients with PR had among the lowest numbers of expanded CD4 and CD8 clones (CD4: 4 and 2; CD8: 7 and 4).

Conclusion: Enrichment of gene sets associated with immune activation in tumor tissue from patients dosed with PF-8600 provides evidence supporting an active, immunomodulatory mechanism. Peripheral CD4/CD8 T cell populations exhibited clonal expansion in response to dosing with PF-8600 at all dose levels further suggesting a PD effect. However, clinical response did not necessarily correlate with a high number of expanded T cell clones, suggesting that clinical response to OX-40 agonism may be driven by the expansion of select anti-tumor T cell clones rather than a broad expansion of T cell clones in the peripheral blood. The phase I study will continue to evaluate PD changes in the tumor and peripheral blood in dose-expansion cohorts of PF-8600 ± utomilumab.

Citation Format: Adi Diab, Omid Hamid, John A. Thompson, Willeke Ros, Fredericus A. L. M. Eskens, Toshihiko Doi, Siwen Hu-Lieskovan, Hua Long, Tenshang Joh, Shoba Potluri, Xiao Wang, Catherine Fleener, Carrie Turich Taylor, Bishu J. Ganguli, Jeffrey Chou, Anthony B. El-Khoueiry. Pharmacodynamic (PD) changes in tumor RNA expression and the peripheral blood T cell receptor (TCR) repertoire in a phase I study of OX40 agonistic monoclonal antibody (mAb) PF-04518600 (PF-8600) [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 CT010.

The relationship of pharmacodynamics (PD) and pharmacokinetics (PK) to clinical outcomes in a phase I study of OX40 agonistic monoclonal antibody (mAb) PF-04518600 (PF-8600)

3027

Background: PF-8600 is a novel fully human IgG2 agonistic mAb against human OX40, a TNF receptor superfamily member expressed primarily on activated T cells. This ongoing phase 1 study (NCT02315066) is investigating the safety, efficacy, PK and PD of PF-8600 in patients (pts) with solid tumors. Methods: PF-8600 (0.01–10 mg/kg) was given IV every 14d. Expression of free/total OX40 receptor, proliferation marker ki67 and activation markers HLA-DR/CD38 were measured in T cell subsets in peripheral blood by flow cytometry in all pts. CD4, CD8, OX40 and FOXP3 were evaluated in paired tumor biopsies (bx), collected from a subset of pts (≥0.1 mg/kg) at baseline (BL) and Wk6, by immunohistochemistry. Results: As of 21Sep2016, 48 pts with melanoma (n = 14), hepatocellular carcinoma (HCC, n = 19), head and neck squamous cell (n = 6) or renal cell carcinoma (n = 9) enrolled in the dose-escalation cohorts (0.01-3 mg/kg). No immune related adverse events (AE) were reported. The most frequent treatment related AEs in > 3 pts were fatigue (27.1%) and nausea and vomiting (8.3% each); all Gr 1-2. 2 pts had a partial response: melanoma at 0.1 (Pt1) and HCC at 0.3 (Pt2) mg/kg. 25 pts had best ORR (BOR) of stable disease (SD; 3 pts ≥24 wks). A majority of pts at 0.1, 0.3, and 3 mg/kg, including Pt1 and Pt2, had increases in ki67 and HLA-DR/CD38 expression in peripheral CD4+ central memory T cells. Pt1, Pt2 and all pts at ≥0.3 mg/kg had full receptor occupancy. Paired bx were only available from pts with BOR of SD or progressive disease. In 10 pts with available paired tumor bx and defined date of radiographic progression (rPD), longer time to rPD correlated with increases in %OX40+ in bx from BL to Wk6, regardless of dose level, tumor type or prior immunotherapy (R2= 0.52, p = 0.0188); no correlation between rPD and CD4+, CD8+ or FOXP3+ expression changes was observed. Updated efficacy, safety, PK and PD data will be presented. Conclusions: PF-8600 is well tolerated with evidence of single agent efficacy. Initial observations of PD markers that change with treatment and correlate with rPD support efforts to confirm these findings as more clinical outcomes and larger sample sizes become available. Clinical trial information: NCT02315066.

Pharmacokinetic, Pharmacodynamic, and Safety Profile of a Novel Anti-CD28 Domain Antibody Antagonist in Healthy Subjects

We report pharmacokinetics, pharmacodynamics, and safety of a novel anti‐CD28 domain antibody antagonist (lulizumab pegol) in healthy subjects following single‐ or multiple‐dose administration. A minimal anticipated biological effect level approach was used to select a 0.01 mg starting dose for a single‐ascending‐dose (SAD), double‐blind, first‐in‐human study. Part 1 included 9 intravenous (IV; 0.01‐100 mg) and 3 subcutaneous (SC; 9‐50 mg) doses or placebo. In part 2, a keyhole limpet hemocyanin (KLH) immunization was performed in 16 subjects/panel, who received 1 of 3 IV doses (9‐100 mg) or placebo. In a double‐blind, multiple‐ascending‐dose (MAD) study, subjects received SC lulizumab 6.25 mg every 2 weeks, 12.5 mg weekly, 37.5 mg weekly, or placebo. Among 180 treated subjects, 169 completed the studies. Peak concentrations and areas under the curve from time 0 to infinity increased dose proportionally. Estimated SC bioavailability was 68.2%. Receptor occupancy of approximately ≥80% was maintained for ≥2 weeks at ≥9‐mg doses (SAD) and throughout the dosing interval (MAD). IV doses ≥9 mg inhibited antibody production against KLH for 2 weeks. No significant cytokine or immune cell changes were observed. No immunogenicity responses persisted, and there was no correlation to adverse events. Headache occurred in 21 SAD and 4 MAD subjects receiving lulizumab; in the MAD study 5 lulizumab subjects experienced infections. Lulizumab IV or SC was safe at all doses studied, without evidence of cytokine release.

Functional Antagonism of Human CD40 Achieved by Targeting a Unique Species-Specific Epitope

Current clinical anti-CD40 biologic agents include both antagonist molecules for the treatment of autoimmune diseases and agonist molecules for immuno-oncology, yet the relationship between CD40 epitope and these opposing biological outcomes is not well defined. This report describes the identification of potent antagonist domain antibodies (dAbs) that bind to a novel human CD40-specific epitope that is divergent in the CD40 of nonhuman primates. A similarly selected anti-cynomolgus CD40 dAb recognizing the homologous epitope is also a potent antagonist. Mutagenesis, biochemical, and X-ray crystallography studies demonstrate that the epitope is distinct from that of CD40 agonists. Both the human-specific and cynomolgus-specific molecules remain pure antagonists even when formatted as bivalent Fc-fusion proteins, making this an attractive therapeutic format for targeting hCD40 in autoimmune indications.