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Introduction: BTK inhibitors (BTKis) are approved for chronic lymphocytic leukemia (CLL), Waldenström macroglobulinemia (WM), mantle cell lymphoma (MCL), and marginal zone lymphoma (MZL). Disease that progresses on BTKis often has BTK mutations that lead to treatment (tx) resistance; novel BTK-targeting agents that overcome BTKi resistance are needed. BGB-16673 is a heterobifunctional small molecule that binds to BTK and E3 ligase, resulting in BTK degradation via ubiquitination. In preclinical models, BGB-16673 degraded wild-type (WT) BTK and known covalent and noncovalent BTKi-resistant mutant proteins, leading to tumor suppression. Methods: Pts with R/R CLL, WM, MCL, MZL, non-germinal center B-cell diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), or Richter transformation (RT) were eligible for this open-label, first-in-human, phase 1 trial (BGB-16673-101; NCT05006716). Pts must have received ≥2 prior therapies (≥1 for RT) and have an ECOG performance status of 0-2 and adequate end-organ function. In the US and Australia, pts must have received a covalent BTKi (cBTKi) if approved for their disease. BGB-16673 was dosed daily by mouth in 28-day cycles. Escalation using a Bayesian optimal interval design with 6 dose levels (50-600 mg once daily) is planned. Primary objectives are to assess safety/tolerability and establish the maximum tolerated dose (MTD) and recommended phase 2 dose. Key secondary objectives are to assess pharmacokinetics, pharmacodynamics (PD), and preliminary antitumor activity. Safety was assessed according to CTCAE v5.0 (all pts) and iwCLL hematologic toxicity criteria (pts with CLL). Dose-limiting toxicities (DLTs) were assessed in the first 4 weeks. Response was assessed per Lugano criteria for all except CLL (iwCLL 2018 criteria) and WM (iwWM-6 criteria). Results: As of May 26, 2023, 26 pts (10 CLL, 4 MCL, 2 MZL, 4 WM, 4 FL, 1 DLBCL, 1 RT) were enrolled at 5 dose levels (50 mg, 4; 100 mg, 9; 200 mg, 9; 350 mg, 3; 500 mg, 1). Median age was 70.5 y (range, 25-83). Median number of prior therapies was 3.5 (range, 2-9), including cBTKis (n=21; 10 CLL, 4 WM, 4 MCL, 1 MZL, 1 RT, 1 DLBCL), BCL2 inhibitors (n=12; 9 CLL, 2 WM, 1 RT), and noncovalent BTKis (ncBTKis; n=4; 2 CLL, 1 WM, 1 FL). In CLL, del17p/ TP53 mutation (n=8) and unmutated IGHV (n=7) were frequent. Median follow-up was 3.5 mo (range, 0.2-13.9). MTD was not reached. Treatment-emergent AEs (TEAEs) were reported by 88.5% of pts (grade [gr] ≥3, 46.2%; serious, 38.5%). The most common TEAEs were contusion (30.8%; no gr ≥3), pyrexia (23.1%; no gr ≥3), neutropenia/neutrophil count decreased (23.1%; gr ≥3, 15.4%), and lipase increased (23.1%; gr ≥3, 3.8%; all transient and asymptomatic). No hypertension or atrial fibrillation was observed. One pt died from sepsis with possible disease progression. No discontinuations due to AEs occurred. Two pts had dose reductions due to TEAEs (gr 3 hematuria with urinary tract infection and recurrent urothelial carcinoma and gr 2 arthralgia). One DLT occurred in 1 pt at 200 mg (gr 3 maculopapular rash on day 27; after 5-day dose hold, assigned dose was recommenced with persistent gr 1 rash). BGB-16673 exposure increased in a dose-dependent manner. At steady state with doses ≥50 mg daily, BGB-16673 exposure exceeded the calculated half maximal degradation concentration for WT and cysteine 481-mutated BTK for the dosing interval. Preliminary PD data showed deep, sustained reductions in BTK protein levels in peripheral blood and tumor tissue, even at the lowest dose. Most CLL pts experienced lymphocytosis during the first 3 cycles of tx. Twenty of 26 pts (77%) remain on therapy (discontinuation: 4 progressive disease, 2 withdrawal). Of 18 response-evaluable pts, 12 (67%) responded (5/6 CLL, 1/3 MCL, 2/2 MZL, 3/4 WM, 1/2 FL, 0/1 DLBCL; 1 CR in MCL, all others had PR; Figure), including pts who received a cBTKi (n=10) and an ncBTKi (n=2). Responses started at the lowest dose level. All responders remain in response, the longest responder remaining on tx for 60 weeks. Conclusions: Preliminary data from this ongoing, first-in-human study of the novel BTK degrader BGB-16673 demonstrate a tolerable safety profile and clinical responses in heavily pretreated pts with B-cell malignancies, including those with BTKi-resistant disease. Substantial reductions in BTK protein levels in peripheral blood and tumor tissue were also observed, demonstrating proof-of-concept of a strong, on-target effect.

Multiple CD19-directed therapies are available for the treatment of relapsed and refractory (R/R) DLBCL, including CAR T cells, tafasitamab/lenalidomide (TL), and loncastuximab tesirine (lonca-T) (Sermer D., Blood Rev 2023). However, there are few data available on the efficacy of sequential CD19-directed therapies. We performed a retrospective study evaluating all patients with R/R LBCL treated consecutively with TL at 11 institutions from 8/2020 to 8/2022, identifying 178 patients. In this study, we specifically evaluate outcomes in patients who received anti-CD19 therapy prior to or after TL. The primary outcome of interest was progression-free survival (PFS) in TL recipients who previously received CD19-directed CAR T therapy, with overall response rate (ORR), complete response rate (CRR), and overall survival (OS) also evaluated. Outcomes of lonca-T and CAR T after TL therapy were evaluated. Data on CD19 expression was assessed on biopsies after TL; this was determined locally using flow cytometry or immunohistochemistry per institutional protocols. In subgroup analyses, ORR and CRR were compared using Fisher's exact test. PFS and OS were estimated using the Kaplan-Meier method, with differences tested using the log-rank test. Of 178 patients who received TL, 52 had received prior anti-CD19 CAR T therapy, at a median of 7.4 months before TL (Table 1). Median PFS was lower in prior CAR T recipients (1.6 mo, 95% CI 1.1-2.5) vs no prior CAR T (2.1 mo, 95% CI 1.8-3.2), with hazard ratio 1.46 (p = 0.04; Figure 1). Best ORR was lower in patients with prior CAR T exposure (15% vs 33%, p = 0.02) though CRR was not significantly different (15% vs 18%, p = 1.0). We specifically evaluated TL outcomes based on prior response to CAR T, given the previously identified association of refractory disease with poor TL outcomes (Qualls D et al., presented at ASH 2022). Of 19 patients who had progressive disease more than 6 months after CAR T, ORR and CRR to TL therapy were 31.6% (all responses were CRs); in 33 patients with refractory disease (less than CR or relapse within 6 months) after CAR T, ORR and CRR to TL were significantly lower, at 6.1% (p = 0.04). Median PFS after TL was shorter in CAR-refractory than CAR-relapsed disease, at 1.4 vs 3.5 months (HR 2.2, p = 0.02). Of 88 patients who received therapy after TL, 20 (23%) received lonca-T and 14 (16%) received CAR T. Data on survival and initiation of new treatment after CAR T or lonca-T was available, but response and progression data after CAR T or lonca-T therapy is pending. These data allowed an estimate of OS and event-free survival (EFS), defined as survival without initiation of a new treatment after CAR T or lonca-T. With a median 3.9 months' follow-up, median EFS after CAR T administration was 3.7 months (95% CI, 0.9 - 6.5), and median OS was 8.1 months (95% CI, 0.6 - 15.7). In patients who received lonca-T, with median 2.7 months' follow-up from initiation, median EFS was 2.8 months (95% CI, 0.9 - 4.7), and median OS was 3.5 months (95% CI, 1.2 - 5.7). When comparing CAR T and lonca-T to polatuzumab vedotin- or chemotherapy-based therapies after TL, there were no significant differences in OS or EFS. In patients who discontinued TL, 24 had a biopsy a median of 18 days after the last dose of tafasitamab. Of these, 13 (54%) were CD19-positive and 11 (46%) were CD19-negative. All samples obtained more than 21 days after tafasitamab (6/6) were CD19-positive, while 46% obtained within 21 days were CD19-positive. These time-dependent findings may reflect “epitope masking” by tafasitamab rather than CD19 loss, reflecting other recent reports (Fitzgerald K., Leuk Lym 2022; Duell J., Leuk Lym 2022). In patients receiving TL after CAR T, responses and PFS were lower than in patients without prior CAR T therapy; however, with disease that was not refractory to prior CAR T, results were similar to patients who had not had prior CAR T. This may reflect that refractory disease, regardless of prior therapy, is associated with shorter PFS, though the possibility of CD19-mediated mechanisms of resistance remains. Modest EFS and OS were seen in patients receiving CAR T therapy or lonca-T after already receiving TL, though this may also reflect the high-risk disease characteristics of this cohort. Overall, in a high-risk, real-world cohort of TL-treated patients, these data suggest that some patients may benefit from subsequent CD19-directed therapies, but better therapeutic options are needed.

Introduction: Histologic transformation (HT) from follicular lymphoma (FL) to an aggressive lymphoma is infrequent but has unfavorable outcomes. Sarkozy et al. (J Clin Oncol, 2019) reported that approximately half of FL-related deaths within the first decade of diagnosis occurred following HT. Our recent analysis showed heterogeneous outcomes with median overall survival (OS) of 61 months (Day et al., ASH, 2022). Prognostic tools post HT would be clinically useful but development has been limited by small cohort sizes. Factors previously associated with outcomes following HT have included age, time to progression, prior therapy, anthracycline exposure, and early HT. Utilizing the Lymphoma Epidemiology of Outcomes (LEO) Consortium of Real World Evidence (CReWE), we describe patterns of care and evaluate other prognostic factors following HT. Methods: This multicenter observational cohort consists of prospectively enrolled patients in the LEO Cohort, and patients with HT retrospectively identified at LEO centers. Patients diagnosed with biopsy proven grade 1-3A FL at diagnosis, and a subsequent biopsy showing HT to an aggressive lymphoma (FL grade 3B, diffuse large B cell lymphoma [DLBCL], or high-grade B cell lymphoma [HGBCL]) between 2002-2022, were eligible for the study. Patients with a component of FL grade 3B, DLBCL, or HGBCL at diagnosis were excluded. HGBCL was defined as double or triple hit or another aggressive subtype. OS was defined as the time from HT until death from any cause and calculated via Kaplan-Meier. Associations between clinical factors at time of HT and/or diagnosis and OS were evaluated using Cox models. Cause of death was evaluated using a competing risk approach. Results: Overall, 328 patients were confirmed with HT during the study period, 41% were female, and the median age at HT was 63 years (interquartile range [IQR] 56-70). The median time from diagnosis to transformation (TDT) was 35 months (IQR 12-66). At HT, 88% had advanced stage disease (III-IV) and LDH was elevated in 49%, while few patients exhibited B symptoms (5%) and ECOG performance status was >2 in 9%. 23% did not receive systemic therapy prior to HT. For those with prior therapy, the median time from prior therapy to HT was 15 months (IQR 7-39). The most frequent treatment regimens following HT were CD20-CHOP (42%), followed by platinum-based salvage therapy (20%), R-EPOCH (10%), CD20-Benda (8%), R-Mono (4%), and R-Gem-Ox (3%). 50 (15%) patients underwent consolidation with autologous stem cell transplant, 3 underwent allogeneic transplant (30 platinum-based, 15 CD20-CHOP, 5 R-EPOCH, 3 Other), and 2 received CAR T-cell therapy (Figure 1). After median follow-up of 85 months from HT, 170 patients had died; 5-year OS was 52% and median OS was 65 months (95% CI: 55-107). Among 160 patient deaths, cause was most often lymphoma-related (progression, n=107 [63%]; therapy-related, n=14 [7%]) compared to non-lymphoma (n=20, 13%) or missing/unknown causes (n=29, 17%). Clinical factors at the time of HT that were associated with worse OS include: ECOG PS >2, age ≥70, IPI 3-5, and shorter TDT (<24 months), hemoglobin <10 g/dl and elevated LDH. A transformation to HGBCL was also associated with inferior OS (Table 1). OS did not significantly differ by gender, BMI, stage, presence of B-symptoms, absolute lymphocyte count, number of extranodal groups, presence of bulky disease at HT, or response to prior FL treatment. Factors at the time of FL diagnosis that were associated with decreased OS after HT included FLIPI score 3-5 (high risk), FLIPI 2 (moderate risk), and FL grade 3A at diagnosis. Exposure to any systemic therapy for FL prior to HT was associated with shorter OS, with the worst outcomes in patients receiving an anthracycline prior to HT. POD24 to frontline immunochemotherapy was associated with inferior OS after HT (Table 1). Conclusions: Patterns of care in Transformed FL are heterogeneous and vary greatly in intensity. These data confirm previous reports that age, early HT, and any systemic therapies prior to HT are negative prognostic indicators for OS. At HT elevated LDH, low hemoglobin, POD24 status, poor performance status, and HT to HGBCL were associated with poor outcomes following HT. These data provide a basis for future prognostic indices to identify patients with highest risk of lymphoma related mortality for whom study of novel treatments is greatly needed.

Introduction Axicabtagene ciloleucel (axi-cel) is an autologous anti-CD19 Chimeric Antigen Receptor (CAR) T-cell therapy that induces durable responses in patients with relapsed or refractory large B-cell lymphoma. At a median of 63.1 months follow-up on the ZUMA-1 trial, median overall survival (OS) was 25.8 months with 5-year OS and PFS (progression-free survival) estimates of 42.6% (95% CI, 32.8-51.9) and 31.8% (95% CI, 22.9-41.1), respectively (Neelapu, Blood 2023). We previously reported outcomes of axi-cel patients treated with standard of care therapy, including 42% who did not meet eligibility criteria for ZUMA-1 based on co-morbidities (Nastoupil, JCO 2020). Here we report results from this cohort at a median follow up of 58 months, as well as late outcomes of interest. Results The US Lymphoma CAR-T Consortium is comprised of 17 US academic centers who contributed data independent of the manufacturer. Two hundred and ninety-eight patients underwent leukapheresis with intent to manufacture standard of care axi-cel (n=298) as of September 30, 2018. In infused patients (n=275), OS and PFS were calculated from date of infusion. After a median follow-up of 58 months, median OS was 34.9 months (95% CI 23.4 - 44.8) with the OS at 3, 4, and 5 years of 49.1% (95% CI 42.9 - 54.9%), 43% (95% CI 36.8 - 48.9%), and 40.3% (95% CI 34.2 - 46.4%), respectively. The median PFS was 8.7 months (95% CI 5.87 - 16.6) and the 3-,4-, and 5- year PFS were 36.1% (95% CI 30.4 - 41.8%), 30.7 (95% CI 25.2 - 36.4%), and 28.5% (95% CI 23 - 34.2%), respectively. Results of multi-variable modeling were similar to our prior analysis: male sex (HR 1.56, 95% CI 1.08 - 2.27, p =0.02); LDH above the upper limit of normal (HR 1.6, 95% CI 1.12 - 2.30, p = 0.01); ECOG status of 2-4 (HR 2.02, 95% CI 1.33 - 3.07, p = <0.001); and elevated bilirubin > 1.5 (HR 5.68, 95% CI 2.21 - 14.6, p = <0.001) were associated with decreased OS. Factors associated with decreased PFS included male sex (HR 1.68, 95% CI 1.20 - 2.37, p = 0.003), LDH above the upper limit of normal (HR 1.82, 95% CI 1.31 - 2.53, p = <0.001), ECOG status of 2-4 (HR 1.93, 95% CI 1.30 - 2.86, p = 0.001), elevated bilirubin (HR 3.68, 95% CI 1.45 - 9.37, p = 0.006) and receipt of 3 or more prior lines of therapy (HR 1.49, 95% CI 1.03 - 2.13, p = 0.032). We also assessed events of interest including late PFS events and causes of non-relapse mortality (NRM). One hundred and ninety-one PFS events occurred after axi-cel infusion during the follow-up period, 151 due to lymphoma progression and 40 NRM. In the first 12 months post infusion, 131 progression events occurred,13 between 1 and 2 years post infusion, and 7 relapses after 2 years with the latest occurring 46.4 months after infusion. Thirteen NRM events occurred in the 1st year post infusion, 6 between 1- and 2-years post infusion and 21 occurring later than 2 years after infusion. Of the 40 NRM events, 21 were secondary to infection including fungal infections (n = 3, 2 candidemia, 1 candidemia and pneumocystis jiroveci pneumonia), JC encephalitis (n=1) and COVID-19 (n = 2). Nine deaths were attributed to secondary malignancy. Other causes of NRM included cerebral edema (n=1), HLH (n=1), intracranial hemorrhage (n=1), suicide (n=1), and unknown (n=6). The 5-year cumulative risk of relapse was 55.2% and the 5-year risk of non-relapse mortality was 16.2%. Excluding non-melanoma skin cancers, twenty-three of 275 (8%) patients were diagnosed with subsequent malignancy after axi-cel treatment: 14/275 (5%) patients were diagnosed with myeloid malignancies (MDS (n=11), AML (n=2), CMML (n=1)); other malignancies included anal squamous cell carcinoma (ca) (n=1); histiocytic sarcoma (n=1); prostate ca (n=1); endometrial ca (n=1); lung ca (n=1); merkel cell ca (n = 1), mesothelioma (n=1), B-ALL (n = 1), and AITL (n=1). Conclusion This multi-center retrospective study showed similar 5-year results to the ZUMA-1 trial with a 5-year PFS and OS of 28.5% and 40.3%, despite including patients who did not meet ZUMA-1 eligibility criteria based on comorbidities. Non-relapse mortality was primarily due to infection and secondary malignancy. This report supports the curative potential of axi-cel but highlights the competing risk of NRM in this high-risk patient population.

Background: In the past year, multiple studies have demonstrated the drastically increased risk of relapse and death in patients with Acute Myeloid Leukemia (AML) who have persistent FLT3 internal tandem duplication (ITD) mutations detectable in clinical remission by next generation sequencing (NGS). Translating this evidence into a change in clinical practice requires both widely available testing and a clear understanding of the clinical implications of FLT3-ITD detection at defined threshold levels. In the largest of the recent studies (Pre-MEASURE, PMID: 36881031), we performed FLT3-ITD MRD detection in blood DNA collected from 608 patients at the time of first remission (CR1) prior to allogeneic hematopoietic cell transplant (alloHCT). To evaluate cross-assay comparability and the impact of residual disease burden levels, we performed analysis on this cohort using a commercially available FLT3-ITD MRD NGS assay. Methods: Of the 608 patients aged 18 or older from the Pre-MEASURE study who received an alloHCT for FLT3-ITD mutated AML during CR1 at a CIBMTR reporting site in the USA between the years of 2013-2019, patients not experiencing non-relapse mortality and with sufficient DNA from pretransplant blood available were included in this analysis. A commercially available testing kit (IVS, Invivoscribe, San Diego, CA), which can detect FLT3-ITD MRD by NGS for up to 21 patients on one Illumina MiSeq flow cell, was used to establish a workflow following clinical testing standards and validated to detect ITDs down to a variant allele fraction (VAF) of at least 0.005%. Results were compared to those previously reported using an anchored multiplex PCR-based (AMP) targeted NGS assay. Overall survival (OS) and cumulative incidence of relapse were estimated with the day of transplant as time 0 using Kaplan-Meier estimation (log-rank tests) and Cox proportional hazards models. Results: A total of 451 patients were included in this study, of which 173 (38%) experienced relapse (median: 5.2 months; range 0.7-52.1) and 133 (29%) died (median: 10.7 months; range 2-53.8) post-alloHCT. The IVS assay identified 232 FLT3-ITD variants with a median VAF of 0.005% (range 0.0002-44%) and length of 51bp (range 5-228). IVS positive patients had a median of 1 FLT3-ITD variant (range 1-15) and median maximum VAF of 0.01% (range 0.0003-44%). Utilizing the same VAF cutoff of 0.01% for MRD positivity for the IVS test as used in the Pre-MEASURE study, patients testing positive prior to alloHCT exhibited higher rates of relapse (79% vs 31%, p<0.0001) and decreased survival (29% vs 77%, p<0.0001) at 3 years compared to testing negative. These results closely align with those previously reported using the AMP assay (Figure A). The IVS test has a superior limit of detection compared with the AMP test, allowing investigation of alternative VAF thresholds. In total, 151 patients (33.5%) were FLT3-ITD MRD positive by IVS of which only 75 (17%) had VAF ≥0.01%. A threshold-free approach for the IVS test improved the ability to identify patients at risk of relapse, predicting 63% of relapses within 6 months of transplant compared to 43% with the 0.01% cutoff, but resulted in decreased specificity as 42% of all positive patients relapsed within 6 months vs. 57% with the 0.01% VAF cutoff. In multivariable analysis, IVS FLT3-ITD MRD status was associated with both relapse and overall survival (Figure B). Additionally, stratifying patients by their level of residual FLT3-ITD disease burden prior to alloHCT revealed a dose-dependent increase in risk for death (Figure B) and relapse. Any detectable level of residual FLT3-ITD over 0.001% VAF exhibited increased risk, with VAFs ≥0.01% being the highest. Conclusions: In this analysis of patients with AML from the Pre-MEASURE study, we show cross-assay evidence that the detection of residual FLT3-ITD variants in pre-transplant blood during CR1 is associated with significantly increased risk of relapse and death after alloHCT. The highly sensitive assay used in this study could identify ~2/3 of patients who relapsed within 6 months and demonstrated that a dose-dependent correlation between residual FLT3-ITD level and adverse clinical outcomes exists, with VAF ≥0.01% representing the highest risk. This evidence provides strong justification for NGS-based AML MRD clinical testing for persistent FLT3-ITD prior to alloHCT to identify patients at high risk of post-transplant relapse and death.

Slow, deep breathing (SDB) is thought to lead to reductions in blood pressure by decreasing vascular‐sympathetic coupling. Venous Occlusion Plethysmography (VOP) is used to assess forearm blood flow (FBF) (ml/min/100 dl tissue). We used this technique to determine the vasodilatory effect of device‐guided (DG) vs self‐paced (SP) slow, deep breathing. We hypothesized that SP would lead to a larger vasodilation response than DG due to a more profound reduction in vascular‐sympathetic coupling, and that this would be correlated with psychological evaluations. Young, healthy male subjects (Mean age: 20 yr; DG: n=10; SP: n=11) rested supine for 20 minutes (baseline), followed by 20 minutes of SP or DG slow, deep breathing, then completed 20 minutes of endogenous breathing (recovery). At baseline, there was no difference in breathing rate between SP and DG (14.36±1.03 vs 15.39±1.29 breaths per minute, p=0.27) and respiratory rate was reduced to 8.36±0.74 breaths per minute (BPM) in the SP group (p<0.01 compared to baseline) and to 6.37±0.10 BPM in the DG group (p<0.01 compared to baseline). Respiratory rates between the two groups differed significantly during SDB (p<0.01 between groups). There was a significant increase in SP FBF compared to baseline at the end of the 20 minute intervention (p<0.05),while the DG group saw no significant increases. In DG, there was a strong negative correlation with the cognitive interference scores to VOP responsiveness (−0.77; R2=0.591), as well as between the cognitive failure score and VOP responsiveness (−0.61; R2=0.3693). In contrast, the SP groups had positive correlations when comparing VOP responsiveness to cognitive interference (0.1; R2=0.093) or cognitive failure (0.30; R2=0.011). For subjects in either breathing group, those who had an increase in FBF in response to SDB also had reductions in STAI anxiety score after the intervention whereas those with a decrease in FBF to SDB had an increase in anxiety score during the slow breathing (p=0.04). Overall, male subjects have a variable vasodilator responses to two types of SDB practices related to underlying psychological metrics. Our data underscores the importance of psychological metrics in physiological outcomes related to SDB practices.

Abstract Although immune checkpoint inhibition (ICI) has produced profound survival benefits in a broad variety of tumors, a proportion of patients do not respond. Treatment failure is in part due to immune suppressive tumor microenvironments (TME), which is particularly true of hepatocellular carcinoma (HCC). Since oncolytic viruses (OV) can generate a highly immune-infiltrated, inflammatory TME, we developed a vesicular stomatitis virus expressing interferon-ß (VSV-IFNß) as a viro-immunotherapy against HCC. Since HCC standard of care atezolizumab/bevacizumab incorporates ICI, we tested the hypothesis that pro-inflammatory VSV-IFNß would recruit, prime, and activate anti-tumor T cells, whose activity anti-PD-L1 ICI would potentiate. However, in a partially anti-PD-L1-responsive model of HCC, addition of VSV-IFNß abolished anti-PD-L1 therapy. Cytometry by Time of Flight showed that VSV-IFNß expanded dominant anti-viral effector CD8 T cells with concomitant, relative disappearance of anti-tumor T cell populations which are the target of anti-PD-L1. However, by expressing a range of HCC tumor antigens within VSV, the potent anti-viral response became amalgamated with an anti-tumor T cell response generating highly significant cures compared to anti-PD-L1 ICI alone. Our data provide a cautionary message for the use of highly immunogenic viruses as tumor-specific immune-therapeutics by showing that dominant anti-viral T cell responses can inhibit sub-dominant anti-tumor T cell responses. However, by chimerizing anti-viral and anti-tumor T cell responses through encoding tumor antigens within the virus, oncolytic virotherapy can be purposed for very effective immune driven tumor clearance and can generate anti-tumor T cell populations upon which immune checkpoint blockade can effectively work.

Abstract Methylation profiling has revealed unexpected relationships between traditional histopathology-based versus biologically-based classifications of brain tumors. Methylation class pleomorphic xanthoastrocytoma (mcPXA) comprises tumors with the same methylation signature as classical PXA but with additional morphologic patterns, including overlap with glioblastoma (GBM). To characterize mcPXA, we examined epidemiologic, histologic, and molecular features as well as clinical behavior of a cohort (n=313) of tumors matching to mcPXA by the DKFZ classifier (v12 score &gt;= 0.85). Patient median age was 19 (range 1-73) with a female predominance (178 female/135 male). CDKN2A/B homozygous deletion was observed in 273 (87%) cases. In the subset of cases tested for BRAF p.V600E (n=120), 111 (93%) harbored the mutation. Concomitant chr7+/chr10- was observed in 66 (21%) cases. In the subset of cases tested for TERT promoter mutations (n=50), 11 (22%) harbored the mutation, always with co-occurrence of BRAF p.V600E (11/11) and infrequently with chr7+/chr10- (3/11). MGMT promoter methylation was observed in 40 (13%) cases. Overall and progression-free survival (OS, PFS) in mcPXA were similar to grade 2-3 IDH-mutant astrocytoma (A-IDH). Prognostic factors in mcPXA included GBM-like histopathology (defined as cases diagnosed as GBM prior to methylation profiling), concomitant chr7+/chr10-, and MGMT promoter methylation. GBM-like histopathology was associated with shorter OS (p=0.02) and PFS (p&lt; 0.01) compared to cases without GBM-like histopathology. Concomitant chr7+/chr10- was associated with shorter PFS (p=0.02), and MGMT promoter methylation was associated with shorter OS (p=0.03). Our findings demonstrate that mcPXA tumors affect adolescents and young adults, share molecular features of classical PXA, and manifest clinical behavior similar to classical PXA, but subsets of tumors with atypical features (chr7+/chr10-, MGMT promoter methylation, and/or GBM-like histopathology) are more aggressive. The use of a molecular definition of PXA reveals that this tumor type is more common than previously appreciated and warrants in-depth study for therapeutic options.

Abstract H3K27M-mutant diffuse midline glioma (DMG) patients have no proven effective therapies beyond radiation. ONC201, a mitochondrial protease ClpP agonist, has recently demonstrated efficacy in these patients, but the mechanism behind this remains unknown. We assessed clinical outcomes, tumor sequencing, and tissue samples from patients treated in two completed multi-site clinical studies (n=71). Patients treated with ONC201 monotherapy following initial radiation but prior to recurrence (n=35) demonstrated a median overall survival of 21.7 months and a median progression-free survival of 12.2 months. Radiographic response was associated with increased expression of key tricarboxylic acid cycle-related genes in baseline tumor sequencing. Similar survival benefits were observed using in utero electroporation and orthotopic mouse models of H3K27M-DMG (median 107 versus 77 days [p=0.02] and median 97 versus 141 days [p=0.004], respectively). Integrated transcriptomic and metabolomic analysis of ONC201-treated H3K27M-DMG cells revealed downregulation of TCA cycle, glycolysis, and pyruvate metabolism genes, most notably oxoglutarate dehydrogenase (OGDH), and concomitant changes in levels of associated metabolites including ɑ-ketoglutarate (ɑ-KG). Interestingly, L-2-hydroxyglutarate (L-2HG), a known inhibitor of the Jumonji C domain family of histone lysine demethylases, was also increased. This corresponded with increases in repressive H3K27me3 in vitro and in human tumors accompanied by epigenetic downregulation of cell cycle regulation and neuro-glial differentiation genes. Genetic knockdown of OGDH recapitulated ONC201-mediated increases in H3K27me3. In contrast, genetic knockdown of ClpP or lactate dehydrogenase A or overexpression of L-2-hydroxyglutarate dehydrogenase (L-2HGDH), but not D-2HGDH, abrogated ONC201-mediated increases in H3K27me3, demonstrating that ONC201 induces the production of L-2HG in H3K27M-DMG cells leading to increased H3K27me3. Overall, our data demonstrates the efficacy of ONC201 in H3K27M-mutant DMG and supports ONC201 as the first monotherapy to improve outcomes in patients with H3K27M-mutant DMG for whom few therapeutic options currently exist. Mechanistically, ONC201 disrupts integrated metabolic and epigenetic pathways and reverses pathognomonic H3K27me3 reduction.