A Phase II Study of Epacadostat and Pembrolizumab in Patients with Advanced Sarcoma

PURPOSE

Epacadostat, an indole 2,3 dioxygenase 1 (IDO1) inhibitor, proposed to shift the tumor microenvironment toward an immune-stimulated state, showed early promise in melanoma but has not been studied in sarcoma. This study combined epacadostat with pembrolizumab, which has modest activity in select sarcoma subtypes.

PATIENTS AND METHODS

This phase II study enrolled patients with advanced sarcoma into five cohorts including (i) undifferentiated pleomorphic sarcoma (UPS)/myxofibrosarcoma, (ii) liposarcoma (LPS), (iii) leiomyosarcoma (LMS), (iv) vascular sarcoma, including angiosarcoma and epithelioid hemangioendothelioma (EHE), and (v) other subtypes. Patients received epacadostat 100 mg twice daily plus pembrolizumab at 200 mg/dose every 3 weeks. The primary endpoint was best objective response rate (ORR), defined as complete response (CR) and partial response (PR), at 24 weeks by RECIST v.1.1.

RESULTS

Thirty patients were enrolled [60% male; median age 54 years (range, 24-78)]. The best ORR at 24 weeks was 3.3% [PR, n = 1 (leiomyosarcoma); two-sided 95% CI, 0.1%-17.2%]. The median PFS was 7.6 weeks (two-sided 95% CI, 6.9-26.7). Treatment was well tolerated. Grade 3 treatment-related adverse events occurred in 23% (n = 7) of patients. In paired pre- and post-treatment tumor samples, no association was found between treatment and PD-L1 or IDO1 tumor expression or IDO-pathway-related gene expression by RNA sequencing. No significant changes in serum tryptophan or kynurenine levels were observed after baseline.

CONCLUSIONS

Combination epacadostat and pembrolizumab was well tolerated and showed limited antitumor activity in sarcoma. Correlative analyses suggested that inadequate IDO1 inhibition was achieved.

Pilot study of bempegaldesleukin in combination with nivolumab in patients with metastatic sarcoma

PD-1 blockade (nivolumab) efficacy remains modest for metastatic sarcoma. In this paper, we present an open-label, non-randomized, non-comparative pilot study of bempegaldesleukin, a CD122-preferential interleukin-2 pathway agonist, with nivolumab in refractory sarcoma at Memorial Sloan Kettering/MD Anderson Cancer Centers (NCT03282344). We report on the primary outcome of objective response rate (ORR) and secondary endpoints of toxicity, clinical benefit, progression-free survival, overall survival, and durations of response/treatment. In 84 patients in 9 histotype cohorts, all patients experienced ≥1 adverse event and treatment-related adverse event; 1 death was possibly treatment-related. ORR was highest in angiosarcoma (3/8) and undifferentiated pleomorphic sarcoma (2/10), meeting predefined endpoints. Results of our exploratory investigation of predictive biomarkers show: CD8 + T cell infiltrates and PD-1 expression correlate with improved ORR; upregulation of immune-related pathways correlate with improved efficacy; Hedgehog pathway expression correlate with resistance. Exploration of this combination in selected sarcomas, and of Hedgehog signaling as a predictive biomarker, warrants further study in larger cohorts.

Presence of immune infiltrates, increased expression of transposable elements, and viral response pathways in sarcoma associate with response to checkpoint inhibition

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Background: Response to checkpoint inhibition (CPI) in sarcoma is overall low and varies between and within subtypes. Understanding tumor intrinsic determinants of this response may improve efficacy and patient selection. The de-repression of transposable elements (TEs), which are epigenetically silenced repetitive DNA elements of viral origin, is linked to anti-tumor immunity through an antiviral inflammatory response. We hypothesize that baseline expression of TEs and epigenetic regulators correlates with overall response rate (ORR) in sarcoma CPI clinical trials. Methods: This is a retrospective analysis of bulk RNA-sequencing data from pre-treatment biopsies of patients on CPI trials in sarcoma (pembrolizumab plus talimogene laherparepvec, nivolumab plus bempegaldesleukin, and pembrolizumab plus epacadostat). Sixty-seven samples from unique patients representing 12 subtypes were analyzed. The MCP counter deconvolution method and unsupervised clustering were used to group samples by immune phenotypes resulting in immune ‘hot’ and ‘cold’ clusters. ORR was defined by RECIST. To determine if baseline expression of TEs and epigenetic regulators significantly predicted immune types, we implemented a lasso penalized logistic regression. Results: Immune ‘hot’ tumors were characterized by increased immune infiltrates including CD8+ T-cells, B-cells, and NK cells vs ‘cold’ tumors. Patients with ‘hot’ vs ‘cold’ tumors had an ORR of 30.5% (11/36) vs. 3.2% (1/31) (p = 0.003; chi-squared). The best predictors of ‘hot vs ‘cold’ was the increased expression of multiple TE families including MER45A, MER57F, and LTR21B (respective lasso coefficients, 0.27, 0.07, and 0.07). Expression of IKZF1, a chromatin-interacting transcription factor, was also predictive (lasso coefficient, 0.35) and increased expression correlated with improved ORR (p = 0.003; unpaired t-test). TE and IKFZ1 expression was significantly correlated with CD8+ T-cell signaling and antiviral response pathways such as cGAS-STING (MER57F, r2= 0.43, padj = 1.75E-4; IKZF1, r2= 0.63, padj = 6.28E-9) and type II interferon (MER57F, r2= 0.67, padj = 2.51E-10; IKZF1, r2= 0.60, padj = 7.19E-8). Increased expression of cGAS-STING (p = 3.9E-4; unpaired t-test) and type II interferon pathways (p = 1.89E-10; unpaired t-test) was significant in ‘hot’ tumors. Conclusions: Immune ‘hot’ baseline immune profiles of sarcoma are associated with improved ORR to CPI and with increased expression of TEs and IKZF1. These differences in gene expression correlate with increased inflammatory signaling, which suggests a response to TE-encoded viral-like sequences that are typically epigenetically silenced. Induction of TE de-repression and IKZF1 expression through epigenetic targeting warrants pre-clinical investigation as a strategy to promote CPI response in sarcomas.

A phase I/II trial of the PD-1 inhibitor retifanlimab (R) in combination with gemcitabine and docetaxel (GD) as first-line therapy in patients (Pts) with advanced soft-tissue sarcoma (STS)

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Background: In a phase III trial, GD had similar response and survival rates to doxorubicin when administered as first-line therapy to advanced STS pts. G and D have each demonstrated synergy with PD-1 blockade in pre-clinical or clinical studies. We hypothesized that GD plus R would be safe, tolerable, and have synergistic activity in STS. Methods: This is an ongoing open-label, single-center, phase I/II trial of R (INCMGA00012) combined with GD in pts with treatment-naïve unresectable or metastatic high-grade STS. Herein, we report the phase I results, which included a safety run-in followed by a 3+3 dose de-escalation design. G (900 mg/m2) was administered on days 1 and 8 and D (75 mg/m2) on day 8, in 21-day cycles. R (210 mg IV flat dose on the run-in portion and 375 mg on the dose de-escalation portion) was administered on day 1 of each cycle starting in cycle 2 and continued as monotherapy after completion of 6 cycles of GD. The primary endpoint of the phase I was to determine the recommended phase 2 dose (RP2D) of R plus GD. Secondary endpoints included describing the safety, assessing best overall response rate (ORR) by RECIST 1.1, disease control rate (DCR), and progression-free survival (PFS). Results: Thirteen pts were treated, 7on the run-in and 6 on the de-escalation portion. One pt progressed prior to starting R and was replaced. Median pt age was 53 (range 28 – 74) and 7 were female. Histologies included leiomyosarcoma (n = 6), undifferentiated pleomorphic sarcoma (2), dedifferentiated liposarcoma (2), pleomorphic liposarcoma (1), angiosarcoma (1), and myxofibrosarcoma (1). The Table lists treatment-related adverse events (TRAEs) that occurred in ≥ 20% pts in descending order of frequency. Additional Grade (Gr) 3 TRAEs occurring in 1 pt each, included: infusion reaction, leukopenia, anorectal infection, neutropenia, and pyelonephritis. Gr 3 pyelonephritis was the only dose-limiting toxicity. There were no Gr ≥ 4 TRAEs. One pt (Gr 3 elevated AST/ALT) required corticosteroids and cessation of study therapy. The RP2D was determined to be 375 mg of R plus GD. Twelve pts were evaluable for response. ORR was 17% (1 of 6; 95% CI 1 - 64%) and 50% (3 of 6; 95% CI 19% - 81%) in the run-in and de-escalation cohorts, respectively. DCR was 100% (6 of 6; 95% CI 52 - 100%) and 83% (5 of 6; 95% CI: 36 - 99%). PFS rates at 24 weeks were 60% (95% CI: 29 - 100%) and 44% (95% CI: 17 - 100%). Conclusions: R plus GD was generally safe and well tolerated with no unexpected safety signals to date. The phase II portion evaluating efficacy of R plus GD at the RP2D is ongoing. Clinical trial information: NCT04577014. [Table: see text]

A Phase I Study of Binimetinib (MEK162) Combined with Pexidartinib (PLX3397) in Patients with Advanced Gastrointestinal Stromal Tumor

Lessons Learned.

The combination of pexidartinib and binimetinib was safe and tolerable and demonstrated encouraging signs of efficacy in two patients with advanced gastrointestinal stromal tumor (GIST) refractory to tyrosine kinase inhibitors (TKIs).

Molecular profiling of GISTs at diagnosis and upon progression may provide insight into the mechanisms of response or resistance to targeted therapies.

Additional trials are needed to further explore combined KIT and MEK inhibition in treatment‐naïve and TKI‐refractory patients with advanced GIST.

Background.

Nearly all patients with advanced gastrointestinal stromal tumor (GIST) develop resistance to imatinib, and subsequent treatments have limited efficacy. Dual inhibition of KIT and MAPK pathways has synergistic antitumor activity in preclinical GIST models.

Methods.

This was an investigator‐initiated, phase I, dose escalation study of the MEK inhibitor binimetinib combined with pexidartinib, a potent inhibitor of CSF1R, KIT, and FLT3, in patients with advanced or metastatic GIST who progressed on imatinib. The primary endpoint was phase II dose determination; secondary endpoints included safety, tolerability, and efficacy. An expansion cohort to further evaluate safety and efficacy was planned.

Results.

Two patients were treated at dose level one (binimetinib 30 mg b.i.d. and pexidartinib 400 mg every morning and 200 mg every evening), after which the study was terminated by the manufacturer. No dose‐limiting toxicities (DLTs) were reported, and treatment was well tolerated. The only grade ≥3 treatment‐emergent adverse event (TEAE) was asymptomatic elevated creatine phosphokinase (CPK). Both patients had a best response of stable disease (SD) by RECIST. Progression‐free survival (PFS) and overall survival (OS) were 6.1 and 14.6 months, respectively, in one patient with five prior lines of therapy. The second patient with NF1‐mutant GIST had a 27% decrease in tumor burden by RECIST and remains on study after 19 months of treatment.

Conclusion.

Pexidartinib combined with binimetinib was tolerable, and meaningful clinical activity was observed in two imatinib‐refractory patients.

Pilot study of NKTR214 and nivolumab in patients with sarcomas

11010

Background: Monotherapy checkpoint inhibitors have minimal efficacy in most patients with metastatic sarcoma. NKTR-214 is a CD122-preferential IL-2 pathway agonist that activates and expands natural killer and CD8+ T cells. Phase I/II data demonstrated the safety and efficacy of nivolumab plus NKTR-214 in multiple tumor types. A trial of NKTR-214 plus nivolumab was initiated in patients with selected sarcomas. Methods: This is a multi-center pilot study enrolling patients (pts) failing prior regimens within 9 cohorts: leiomyosarcoma (LMS), undifferentiated pleomorphic sarcoma (UPS), dedifferentiated liposarcoma (DDLPS), chondrosarcoma (CS), osteosarcoma (OS), angiosarcoma (AS), alveolar soft part sarcoma (ASPS), synovial sarcoma/small blue round cell and other. Pts received NKTR 0.006mg/kg with nivolumab 360 mg every 3 weeks. Primary endpoint was objective response rate (ORR), secondary endpoints were adverse events (AEs), progression-free, overall survival (PFS,OS) and clinical benefit rate (CBR.) Pre/on treatment biopsies performed on patients for correlative studies including PD-L1 expression and TIL characterization by immunohistochemistry, whole exome sequencing and RNAseq. Results: Enrollment completed with 10 patients in cohorts below. 50 pts enrolled (median age 58, range 14-80), 54% female. Median follow-up time is 13m. 50% of patients were refractory ≥3 lines of therapy. Grade 3/4 treatment related adverse events occurred in 26% of patients. 2% of patients stopped due to AEs. Median time to response was 3.6m. Responses seen in LMS, UPS, dedifferentiated CS; on-going in UPS/CS. Prolonged disease stability in DDLPS. 6 patients remain on treatment. Conclusions: Nivolumab plus NKTR-214 was safe and tolerable in heavily pre-treated and refractory sarcoma patients. Responses were protracted overtime; on-going in UPS and dedifferentiated CS. Prolonged disease stability seen in DDLPS in patients. All correlative analyses are in progress and will be presented. Enrollment continues with plans to add a treatment naïve cohort. Clinical trial information: NCT03282344. [Table: see text]

Somatic mutational profile of Merkel cell carcinoma treated with immune checkpoint blockade: Preliminary results from a planned multiplatform analysis

e21064

Background: Merkel cell carcinoma (MCC) is an immunogenic neuroendocrine malignancy with promising responses to immune checkpoint blockade (ICB). Although ICB is standard of care in advanced MCC patients, approximately 50% of patients are resistant to ICB. Thus, it is crucial to identify biomarkers predictive of response. Methods: To understand the genomic landscape of MCC, we performed exome capture sequencing on 27 tumor and matched normal samples from 25 patients with MCC treated at Memorial Sloan Kettering. Herein, we report the analysis of 16 paired samples from 14 patients. Nonsynonymous, high-confidence somatic mutations were identified and tumor reads aligned to the Merkel cell polyoma virus (MCPyV) were quantified. Results: Tumor and matched normal samples were sequenced to a median target coverage depth of 53x and 79x reads, respectively. One sample was not analyzed due to inadequate coverage. The MCPyV genome was detected in 12 of 13 patients (92%). The median somatic mutation burden among analyzed samples was 19 nonsynonymous variants per exome (range: 8 - 120). No recurrent driver mutations were identified in any sample. Four samples lacked potential driver mutations and, among the remaining 11 samples, 36 putatively oncogenic mutations were detected in 33 genes (variant allele frequency: 0.08 – 1), including genes involved in the cell cycle checkpoint ( TP53, RB1), DNA damage repair ( ERCC4, FANCA, FANCD2), PI3K-AKT-mTOR ( PIK3CA, PIK3CG), and Notch ( NOTCH1, NOTCH2) pathways. One sample with undetected MCPyV DNA demonstrated loss of heterozygosity of both TP53 and RB1. Four samples contained strand coordinated clusters of mutations in more than 20 distinct gene regions, suggesting an APOBEC-high mutagenesis signature. Conclusions: The MCPyV genome was detected in most tumors analyzed and tumor mutation burden was low in such tumors, consistent with published literature. Analysis of an additional 11 sample pairs is ongoing, along with personalized neoantigen binding predictions on all samples. Immunohistochemistry (IHC) for PDL1 and CD8 expression is in progress. Associations between the aforementioned and response to ICB will be reported.

A phase II study of epacadostat and pembrolizumab in patients with advanced sarcoma

11049

Background: Tumors express IDO1, an intracellular enzyme involved in the degradation of tryptophan to kynurenine, in order to evade immunosurveillance. Epacadostat inhibits IDO1 and shifts the tumor microenvironment from an immunosuppressive state to an immune-stimulated state. Pembrolizumab previously demonstrated activity in select sarcoma subtypes. We performed an open-label, single-center, phase II study of epacadostat and pembrolizumab in patients with advanced sarcoma. Methods: Patients received the recommended phase II dose of oral epacadostat (100mg) twice per day and intravenous pembrolizumab (200mg/dose) every 3 weeks. The primary endpoint was best objective response rate (ORR) (complete response and partial response [PR]) at 24 weeks by RECIST 1.1. Secondary endpoints included adverse events (AEs), ORR by irRECIST, progression free survival (PFS) and overall survival (OS). Correlative studies performed on pre/on-treatment biopsy specimens included PD-L1, IDO1, and kynurenine expression and characterization of tumor infiltrating lymphocytes by IHC, whole exome and RNA sequencing. Results: Twenty-nine patients were enrolled [median age 53 years (range, 24-78), 57% male, ECOG PS 0 83%]. Histological subtypes included leiomyosarcoma (17%), UPS (17%), myxofibrosarcoma (7%), liposarcoma (10.5%), EHE (10.5%), angiosarcoma (3%), “other” sarcoma subtype (35%). Patients were refractory to 0 (21%), 1 (38%), 2 (24%) and ≥ 3 (17%) prior lines of therapy. The most common ( > 20% of pts) grade (G)1 or 2 treatment related AEs (TRAEs) observed included fatigue (31%), rash (31%) and ALT elevation (24%). G3 TRAEs included AST elevation (10%), ALT elevation, anemia, hypophosphatemia and increased lipase each occurred in 3% of pts. Three patients discontinued therapy due to G3 immune mediated hepatitis. Among the 29 evaluable patients 1 (3%) confirmed PR (leiomyosarcoma), 13 stable diseases (45%) and 15 progressions (52%) were observed by RECIST 1.1. The median PFS was 8.0 weeks (two-sided 95% CI: 6.9 ~ 26.7) and the PFS rate at 24 weeks was 27.9% (two-sided 95% CI: 15.0% ~ 52.2%). The median OS was not estimable (two-sided 95% CI: 40.9 weeks ~ NE). The OS at 24 weeks was 85.2% (95% CI: 72.8%, 99.7%). Conclusions: Epacadostat in combination with pembrolizumab was generally well tolerated. Limited anti-tumor activity was observed among advanced sarcoma patients. Correlative analyses including determination of adequacy of IDO1 inhibition will be reported. Clinical trial information: NCT03414229.

Helping undergraduates repair faulty mental models in the student laboratory

Over half of the undergraduate students entering physiology hold a misconception concerning how breathing pattern changes when minute ventilation increases. Repair of this misconception was used as a measure to compare the impact of three student laboratory protocols on learning by 696 undergraduate students at 5 institutions. Students were tested for the presence of the misconception before and after performing a laboratory activity in which they measured the effect of exercise on tidal volume and breathing frequency. The first protocol followed a traditional written "observe and record" ("cookbook") format. In the second treatment group, a written protocol asked students to complete a prediction table before running the experiment ("predictor" protocol). Students in the third treatment group were given the written "predictor" protocol but were also required to verbalize their predictions before running the experiment ("instructor intervention" protocol). In each of the three groups, the number of students whose performance improved on the posttest was greater than the number of students who performed less well on the posttest (P < 0.001). Thus the laboratory protocols helped students correct the misconception. However, the remediation rate for students in the "instructor intervention" group was more than twice that observed for the other treatment groups (P < 0.001). The results indicate that laboratory instruction is more effective when students verbalize predictions from their mental models than when they only "discover" the outcome of the experiment.

How accurate are our assumptions about our students' background knowledge?

Teachers establish prerequisites that students must meet before they are permitted to enter their courses. It is expected that having these prerequisites will provide students with the knowledge and skills they will need to successfully learn the course content. Also, the material that the students are expected to have previously learned need not be included in a course. We wanted to determine how accurate instructors' understanding of their students background knowledge actually was. To do this, we wrote a set of multiple-choice questions that could be used to test students' knowledge of concepts deemed to be essential for learning respiratory physiology. Instructors then selected 10 of these questions to be used as a prerequisite knowledge test. The instructors also predicted the performance they expected from the students on each of the questions they had selected. The resulting tests were administered in the first week of each of seven courses. The results of this study demonstrate that instructors are poor judges of what beginning students know. Instructors tended to both underestimate and overestimate students' knowledge by large margins on individual questions. Although on the average they tended to underestimate students' factual knowledge, they overestimated the students' abilities to apply this knowledge. Hence, the validity of decisions that instructors make, predicated on the basis of their students having the prerequisite knowledge that they expect, is open to question.

Aneurysm recurrence associated with induced hypertension and hypervolemia

A case of angiographic recurrence of a previously clipped large distal basilar aneurysm associated with prolonged hypervolemic and hypertensive therapy for vasospasm is reported. Currently, the most effective therapy for reversing neurological deficits secondary to vasospasm and for augmenting cerebral blood flow is induced hypertension and hypervolemia. The complication of aneurysm enlargement with this therapeutic modality has been postulated but not previously demonstrated.

Biphasic association of p-nitrophenyl 2-O-alpha-D-mannopyranosyl-alpha-D-mannopyranoside and concanavalin A as detected by stopped flow spectroscopy

Kinetics of binding of p-nitrophenyl 2-O-alpha-D-mannopyranosyl-alpha-D-mannopyranoside (M2) to concanaviln A (con A) were examined. The time course of formation of a M2 . con A complex is clearly biphasic, whereas the association with con A of p-nitrophenyl 2-O-methyl-alpha-D-mannopyranoside and other monosaccharides is a monophasic process. The biphasic time course of the binding of M2 to conA is most simply explained in terms of a model wherein the disaccharide can bind to con A two different ways. In the initial rapid phase of the biphasic reaction, both complexes form in amounts determined by the relative values of the rate constants for association. In the subsequent slow phase, the complexes equilibriate according to the relative values of the initial constants for formation of each complex. The enthalpy of activation for formation of the initial complexes with M2 is about 4 kcal/mol less favorable than for monosaccharides, whereas the entropy of activations about 14 e.u. more favorable for binding of the disaccharide. These differences in the activation parameters for binding M2 and monosaccharides suggest that con A interacts simultaneously with groups on both mannopyranosyl residues.