Recurrent high-grade gliomas are aggressive brain tumors with a poor prognosis. They remain an unmet medical need, in part because of an incomplete understanding of the immunosuppressive tumor microenvironment. Although immune checkpoint inhibitors targeting programmed death 1 (PD-1) may have a therapeutic role, their efficacy may be limited by a paucity of tumor-infiltrating lymphocytes. Recently, the Controlled IL-12 gene therapy system has shown promise in increasing glioma immunogenicity. This system stimulates local IL-12 production through a locally administered adenoviral vector, which delivers genetic information for IL-12 and a transcription switch. An orally administered activator ligand, veledimex (VDX), controls transcription levels. IL-12 activity leads to downstream production of IFN-. and increases tumor immunogenicity.1 A recent phase 1 clinical trial showed that Controlled IL-12 therapy was associated with increased expression of PD-1 and PD-L1 in tumor-associated T-cell infiltrates in glioma.1 This supports the concept of investigating Controlled IL-12 in combination with immune checkpoint inhibitor therapy. Here, we describe the case of a patient with a recurrent grade 4 astrocytoma in which post-temozolomide (TMZ) DNA mismatch repair (MMR)-deficient tumor subclones disappeared following administration of Controlled IL-12 with PD-1 blockade. These data demonstrate that the immune system can be engaged to target high-grade glioma.

Ad-RTS-hIL-12 (Ad) is a gene therapy candidate for intratumoral (IT) delivery that conditionally expresses IL-12 (IL-12) under the transcriptional control of orally administered veledimex (V) acting via the RheoSwitch Therapeutic Systemâ gene switch. Increased PD-1 expression in samples of rGBM following Ad+V (ASCO 2020) supports combination immunotherapy with a PD-1 inhibitor. Phase 1 trials in rGBM of Ad+V as monotherapy and in combination with PD-1 inhibitor revealed encouraging safety and survival data. This phase 2 trial (NCT04006119) in adults with rGBM is evaluating safety and efficacy (overall survival) of Ad + V with pre/post-operative cemiplimab-rwlc (cemi) 350 mg IV, Days -7, 15, then Q3W; Ad single IT injection (2 x 1011 viral particles, day of resection (Day 0) /craniotomy); and V (20 mg PO, Days 0–14). Longitudinal sampling of serum assessed IL-12 and endogenous cytokines production. Anti-tumor effects were described upon preliminary review. Serial MRI evaluated tumor response. Follow-up described overall survival. Initial safety data (51 unique adverse reactions in 28 subjects) appeared similar to Ad+V and the cemi label, respectively, being manageable without synergistic toxicities and generally reversible. Of 35 SAEs reported in 18 subjects, 10 SAEs in 7 subjects were related to Ad+V. IL-12 and IFN-g levels increased after Ad+V administration peaking on Day 3 at 34 ± 11 pg/mL and 13 ± 5 pg/mL (mean ± SEM), respectively. Immune-mediated anti-tumor effects were noted, including a post-treatment biopsy to rule out progression which demonstrated an immune infiltrate consistent with pseudoprogression and loss of tumor cell heterogeneity suggesting immunoediting. Enrollment is anticipated to be completed in 2Q2020 with follow-up ongoing and initial survival data will be presented. V crossed the blood-brain barrier to produce functional IL-12. Controlled IL-12 therapy and cemi is a rational combination with initial data consistent with immune-mediated anti-tumor effects with a favorable safety profile.

DIPG, which is the leading cause of pediatric brain cancer death with no effective treatment, has neither a highly immunosuppressive nor inflammatory tumor microenvironment (TME). Therefore, eliciting a pro-inflammatory TME may provide therapeutic benefit. We previously demonstrated in adults with recurrent glioblastoma that loco-regional delivery of interleukin 12 administered under the control of the proprietary transcriptional switch RheoSwitch Therapeutic Systemâ (RTSâ) delivered via a replication-incompetent adenovirus (“Controlled IL-12”) turned “cold” tumors “hot” for up to 5.8 months (Sci Transl Med. 2019;11(505)) and seemed to improve median overall survival as compared with historical controls (SNO 2020). A multicenter, phase I/II, open-label study (NCT03330197) is determining the safety and tolerability of Ad (2 x 1011 viral particles) administered by stereotactic intratumoral injection (Day 0) and 14 daily (Days 1 to 14) V doses (10 or 20 mg, body surface area adjusted). The first DIPG subject enrolled was in April 2020 with completion of the first cohort (arm 1, n=3) enrollment anticipated by September 2020. The first subject has tolerated treatment well with no SAEs during the evaluation period. Endogenous serum cytokines increased (including IFN-g 11.4 pg/mL, Day 3), consistent with V crossing the blood-brain barrier and activating the RTSâ switch to conditionally produce recombinant IL-12. Other biomarkers include plasma PK and circulating DNA. Follow-up is ongoing and enrollment is proceeding. Since development of effective immunotherapy for DIPG likely depends on eliciting a tumor-specific effector immune response, Controlled IL-12 is a promising immunotherapy candidate. The first DIPG subject shows encouraging data on safety, tolerability, serum cytokines and early signs consistent with a clinical response. After completion of dose-escalation, the study may be expanded up to 30 patients, which will be considered the phase II component of the study.

A published clinical trial of veledimex (V)-regulatable interleukin-12 (IL-12) gene therapy (“Controlled IL-12”) under the control of a transcriptional switch (RheoSwitch Therapeutic Systemâ, RTSâ) as monotherapy in recurrent glioblastoma (rGBM) showed sustained infiltration of activated T cells within the tumor months after treatment (Sci Transl Med. 2019;11(505)). These T cells demonstrated up-regulation of immune checkpoint signaling, providing a rationale for combination therapy with the PD-1 inhibitor, nivolumab (nivo). We report interim findings following completion of enrollment (with follow-up ongoing) for a multi-institutional, open label, dose-escalation phase 1 trial (NCT03636477) evaluating safety and tolerability of loco-regional Controlled IL-12 in combination with nivo in adults with rGBM. Replication-incompetent adenovirus coding for RTS-IL-12 (Ad) was administered during surgery by free-hand injection into the tumor and periphery (2 x 1011 viral particles, Day 0) accompanied by V (10 or 20 mg) PO QD x 15 (Days 0 to 14) in combination with nivo (1 or 3 mg/kg) IV on Days -7, 15, then Q2W. Twenty-one subjects were treated (Cohort 1: V 10 mg, nivo 1 mg/kg, n=3; Cohort 2: V 10 mg, nivo 3 mg/kg, n=3; and Cohort 3: V 20 mg, nivo 3 mg/kg, n=3 & 12 in expansion). Safety data were comparable to Ad+V monotherapy. Adverse reactions (ARs) during follow-on nivo dosing were consistent with nivo labeling. ARs were manageable and generally reversible with no synergistic toxicities. Updated overall survival findings will be presented. Baseline and post-treatment histochemical staining and multiplex immunofluorescence analyses for a subgroup of subjects will be discussed. The safety of this combination immunotherapy has been established, leading to a currently accruing phase 2 clinical trial of loco-regional Controlled IL-12 gene therapy in combination with the PD-1 inhibitor cemiplimab-rwlc (NCT 04006119).

Ad-RTS-hIL-12 (Ad) is a novel gene therapy, conditionally expressing IL-12 via the RheoSwitch Therapeutic System® (RTS®) gene switch under control of an oral activator ligand, veledimex (V). We previously reported results from 51 subjects (NCT02026271 and NCT03679754) describing biological activity of controlled IL-12, safety and survival data. Previously, subjects who received Ad+V (20 mg) managed with low-dose dexamethasone in the Main study achieved a mOS of 17.8 months, which is approximately twice the anticipated survival compared to historical controls. The mechanism of action of Ad+V is based on controlled secretion of recombinant IL-12 (measured in peripheral blood as a surrogate for intra-tumor-production), downstream upregulation of endogenous IFN-g (measured in peripheral blood), and an increase in the “cytoindex” (ratio of circulating CD8+ T cells to FoxP3+ regulatory T cells), an emerging biomarker of overall survival. Herein we provide an update of subject characteristics, survival and biomarker analysis from the ongoing Phase 1 and expansion substudy. assessing safety and tolerability of local, inducible IL-12 by single intratumoral injection of Ad (2 x 1011 viral particles) + V (20 mg PO QD x15 doses Days 0–14) in subjects, including a subset receiving low-dose corticosteroids (≤20 mg cumulative dexamethasone Days 0–14). Drug-related toxicities were predictable, dose-related, and promptly reversible upon discontinuation of V with no drug-related deaths. Biomarker studies related to production of IL-12 and IFN-g, as well as cytoindex remain encouraging. As of 04Jun19, mOS in the Expansion substudy had not yet been reached (patient enrollment occurred from September 2018-February 2019). Most subjects (65%) received low-dose dexamethasone (cumulative ≤20mg Days 0–14); initial impact of this and other subject characteristics on survival will be presented.

Monotherapy with intratumoral Ad-RTS-hIL-12 (Ad), a novel gene therapeutic conditionally expressing IL-12 under the transcriptional control of oral veledimex (V, 20 mg) acting via the proprietary RheoSwitch Therapeutic System® (RTS®), was shown in a phase 1 Main study (NCT02026271) to elicit a sustained intra-tumoral activated cytotoxic T-cell response with co-expression of PD-1. Additionally, the Main study showed improved median overall survival (mOS), compared to historical controls, in subjects with recurrent glioblastoma (rGBM) receiving Ad + V. Herein, we report updated findings from on an ongoing open label, dose-escalation Phase 1 substudy (NCT03636477) evaluating safety and tolerability of local, controlled IL-12 plus nivolumab in adult subjects with rGBM. Ad was administered by single intratumoral injection (2 x 1011 viral particles) on Day 0 plus V (10 and 20 mg) PO QD x 15 with nivolumab (1 and 3mg/kg) IV on Days -7, 15, then Q2W. Subjects have been accrued into three cohorts and follow-up is ongoing. Data from all three cohorts regarding dose escalation of V and nivolumab will be presented. The initial safety profile during V dosing period was similar to Ad+V monotherapy with adverse reactions being dose-related and rapidly reversible upon discontinuation of V. And those adverse reactions during the follow on nivolumab dosing were tolerable and manageable and consistent with nivolumab labeling, with no synergistic toxicities, and drug-related deaths. In the first two cohorts (where data is available), combination therapy improved the biomarker “cytoindex” (ratio of circulating CD8+ T cells to FoxP3+ regulatory T cells). (In the Main study, cytoindex correlated with overall survival). Controlled IL-12 production using Ad+V with nivolumab is a rational combination with initial data consistent with immune-mediated anti-tumor effects with a favorable safety profile. Further phase 2 investigation of Ad+V plus a checkpoint inhibitor in rGBM is planned.

Ad-RTS-hIL-12 (Ad) is a novel gene therapy expressing IL-12 via the RheoSwitch Therapeutic System® gene switch under control of an oral activator ligand, veledimex (V). We previously reported on an open label Phase I trial describing biological activity of recombinant IL-12 with downstream IFN-γ and activation of the immune system. We provide an update on the intratumoral injections of Ad (2x1011virus-particles) + V for patients with recurrent GBM (rGBM) in Group 1 (G1) (craniotomy, n=31) and initial results for Group 2 (G2) (stereotactic administration n=7). In G1, the V 20-mg cohort mOS increased to 12.7 months with mean follow-up of 12.9 months. 20-mg V in G1 showed fewer toxicities and higher V compliance (84%) compared with higher-doses of V (30 and 40-mg) with 75% and 67%, respectively. These data are encouraging compared to historical data that predict mOS of 5 to 8 months. An additional cohort at V 10-mg (n=6) was well tolerated, but subtherapeutic, with a mOS of 7.6 months (mean follow-up 6.7 months). There was an association between V dose level, blood-brain-barrier penetration, and drug-related adverse events (AEs) with increased TEAEs observed above V 20-mg. Subgroup analyses across all cohorts did not detect statistically significant differences including extent of resection or IDH mutation status. Subjects (20-mg V) who received a cumulative dose of ≤10mg of dexamethasone during the first 15 days of treatment showed improved OS versus >100mg of dexamethasone, suggesting corticosteroid-mediated blunting of the IL-12 dependent immune-mediated therapeutic effect. In the G2 20-mg V cohort, similar cytokine levels and reversible AEs were observed compared to G1; follow up is ongoing and mOS will be presented. Based on these results and the best risk-benefit profile, the 20-mg V dose level was chosen for further investigation. Combination with an immune checkpoint inhibitor in rGBM is underway.

e20581 Background: Response to anti–PD-L1/PD-1 therapy in patients with NSCLC has been associated with tumor PD-L1 expression. Avelumab is a fully human anti‒PD-L1 IgG1 antibody that has shown antitumor activity in advanced NSCLC, with a trend for greater efficacy in patients with PD-L1+ vs PD-L1– NSCLC tumors, as assessed using a proprietary PD-L1 assay in development (Dako, Carpinteria, CA; based on antibody clone 73-10, Merck KGaA, Darmstadt, Germany). This study compares the analytical performance of the 73-10 assay with the FDA-approved PD-L1 IHC 22C3 pharmDx diagnostic assay (Dako) in NSCLC tumors. Methods: Formalin-fixed paraffin-embedded NSCLC tumor samples were obtained from a commercial source and from a study of first-line (1L) avelumab in patients with advanced NSCLC (NCT01772004). Tumor membrane PD-L1 expression was assessed with the 73-10 and 22C3 assays by immunohistochemistry. Correlation between assays was determined at different PD-L1 cut-off levels. Results: In initial staining of commercial NSCLC samples, the 73-10 assay showed a broad dynamic range. Of 148 commercial samples, the 73-10 assay with ≥1%, ≥50% and ≥80% cut-offs classified 64.2%, 36.5% and 23.6% of samples as PD-L1+, respectively, whereas 20.3% were PD-L1+ with the 22C3 assay at a pre-specified ≥50% cut-off. The overall percentage agreement between assays was 83.8% using the ≥50% cut-off for both assays, and 93.9% using the ≥80% cut-off for 73-10 and ≥50% for 22C3. In follow-up studies, 83 study samples from the 1L NSCLC cohort were evaluable with both assays. With the 73-10 assay at ≥1%, ≥50%, and ≥80% cut-offs, 79.5%, 45.8%, and 31.3% of study tumors, respectively, were PD-L1+; with the 22C3 assay at ≥1% and ≥50% cut-offs, 59.0% and 21.7% were PD-L1+. Conclusions: Using a high tumor cell PD-L1 staining cut-off, the 73-10 and 22C3 assays showed highly concordant staining of NSCLC samples, with similar sensitivity observed with an ≥80% cut-off for 73-10 and ≥50% for 22C3. Using a low frequency of tumor PD-L1 expression, data suggested that the 73-10 assay had greater sensitivity than the 22C3 assay. These results provide a rationale for additional studies using the 73-10 assay at various cut-offs within the avelumab trial program. Clinical trial information: NCT01772004.

4528 Background: Avelumab, a fully human anti‒PD-L1 IgG1 antibody, has shown promising efficacy and safety in 2 cohorts of patients (pts) with mUC. We now report updated data from a pooled analysis of these pts with mUC from JAVELIN Solid Tumor (NCT01772004) and further characterize the clinical activity of avelumab in this disease. Methods: Pts with mUC progressed after platinum-based therapy or cisplatin ineligible received avelumab 10 mg/kg 1-hour IV Q2W. Tumors were assessed every 6 weeks by independent review (RECIST v1.1). Endpoints included objective response rate (ORR), duration of response (DOR), progression-free survival (PFS), overall survival (OS), safety (NCI CTCAE v4.0), and tumor PD-L1 expression. Results: As of Jun 9, 2016, 249 pts had received avelumab for a median of 12 weeks (range 2-92) and were followed up for a minimum of 6 weeks. Primary tumor site was upper tract (renal pelvis/ureter) in 23.3% and lower tract (bladder/urethra) in 76.7%. 242 pts (97.2%) had progressed on prior platinum therapy and 7 pts (2.8%) were platinum naive. In 161 post-platinum pts with ≥6 months of follow-up, confirmed ORR was 17.4% (95% CI 11.9-24.1; complete response in 6.2%) with a disease control rate of 39.8%. Response was ongoing in 23/28 responders at data cut (82.1%; median DOR not reached), and the 24-week durable response rate was 92.3% (95% CI 72.6-98.0). Responses occurred across PD-L1 expression levels tested (≥5% and < 5% tumor cell‒staining [25.4% and 13.2%]). In all post-platinum pts (n = 242), median PFS was 6.6 weeks (95% CI 6.1-11.6), median OS was 7.4 months (95% CI 5.7-10.3) and 6-month OS rate was 54.9 (95% CI 47.7-61.7). Treatment-related adverse events (TRAE) of any grade occurred in 166/249 pts (66.7%); most common (≥10%) were infusion-related reaction (22.9%, all grade ≤2) and fatigue (16.1%). 21 pts (8.4%) had a grade ≥3 TRAE (fatigue [1.6%] and asthenia [0.8%] in > 1 pt). 34 pts (13.7%) had an immune-related AE (grade ≥3 in 2.4%). There was 1 treatment-related death (pneumonitis). Conclusions: Avelumab was well tolerated and showed durable responses in heavily pretreated pts with mUC, irrespective of tumor PD-L1 expression status. Clinical trial information: NCT01772004.