Background

Diffuse gliomas are highly aggressive brain tumors that invariably relapse despite treatment with chemo- and radiotherapy. Treatment with alkylating chemotherapy can drive tumors to develop a hypermutator phenotype. In contrast, the genomic effects of radiotherapy (RT) remain unknown.

Methods

We analyzed the mutational spectra following treatment with RT in whole genome or exome sequencing data from over > 4,000 samples, including 190 paired primary-recurrent gliomas from the Glioma Longitudinal Analysis (GLASS) dataset and 3693 post-treatment metastatic tumors from the Hartwig Medical Foundation.

Results

We identified a significant increase in the burden of small deletions following radiation therapy that was independent of other factors (P=3e-03, log-linear regression model). These novel deletions demonstrated distinct characteristics when compared to pre-existing deletions present prior to RT-treatment and deletions in RT-untreated tumors. Radiation therapy-acquired deletions were characterized by a larger deletion size (GLASS and HMF, P=1.5e-04 and P=6e-16, respectively; Mann-Whitney U test), an increased distance to repetitive DNA elements (P<2.2e-16, Kolmogorov-Smirnov test) and a lack of microhomology at breakpoints (P = 6.6e-05, paired Wilcoxon signed-rank test).

These observations suggested that canonical non-homologous end joining (c-NHEJ) was the preferred pathway for DNA double strand break repair of RT-induced DNA damage. Furthermore, radiotherapy resulted in frequent chromosomal deletions and significantly increased frequencies of CDKN2A homozygous deletions in IDHmut glioma (P=1.9e-05, Fisher’s exact test). Finally, a high burden of RT-associated deletions was associated with worse clinical outcomes (GLASS and HMF, P=3.4e-02 and P<1e-04, respectively; log-rank test).

Conclusions

Our results collectively suggest that effective repair of RT-induced DNA damage is detrimental to patient survival and that inhibiting c-NHEJ may be a viable strategy for improving the cancer-killing effect of radiotherapy. Taken together, the identified genomic scars as a result of radiation therapy reflect a more aggressive tumor with increased levels of resistance to follow up treatments.

Legal entity responsible for the study

The authors.

Funding

NIH.

Disclosure

All authors have declared no conflicts of interest.

Background

This dual-drug phase 0 study (NCT04391595) evaluates the tumor pharmacokinetics (PK) and tumor pharmacodynamics (PD) of abemaciclib, a selective CDK4/6-inhibitor, plus LY3214996, a selective ERK1/2 inhibitor, in recurrent GBM patients.

Methods

Adult recurrent GBM patients (n=10) with intact RB expression, >30% pERK expression, and CDKN2A/B deletion or CDK4/6 amplification received six days of abemaciclib (150mg BID) plus LY3214996 (200mg QD) prior to a planned resection at 3-5 or 7-9 hour time interval after the final drug dose in a Time-Escalation Arm. Tumor tissue (gadolinium [Gd]-enhancing and nonenhancing regions), cerebrospinal fluid (CSF), and plasma were collected. Total and unbound drug concentrations were measured using validated LC-MS/MS methods. Tumor PD effects, including RB and RSK phosphorylation, were compared to matched archival or pre-treatment biopsied tissue. A PK ‘trigger’ (i.e., unbound concentration > 5x biochemical IC₅₀) was set for each drug. Gd-nonenhancing tumor tissue exhibiting abemaciclib and LY3214996 concentrations in excess of their trigger threshold qualified patients for postoperative dual-drug therapy.

Results

No dose-limiting toxicities were observed. In Gd-nonenhancing tumor regions, median unbound concentrations of abemaciclib were 31.2 nM (3-5 hour cohort) and 25.1 nM (7-9 hour cohort) while median unbound concentrations of LY3214996 were 52.0 nM (3-5 hour cohort) and 10.2 nM (7-9 hour cohort). Tumor RB and RSK phosphorylation decreased in 6/10 and 2/10 patients, respectively. Tumor proliferation (MIB-1) was decreased in 8/10 patients. 5/10 patients exceeded PK thresholds for both abemaciclib (12 nM) and LY3214996 (25 nM), thereby entering the study’s therapeutic expansion phase.

Conclusions

Abemaciclib and LY3214996 achieve pharmacologically-relevant concentrations in Gd-non-enhancing GBM tissue and are associated with suppression of the RB pathway and tumor proliferation. The Optimal Time Interval (OTI) for tissue sampling was 3-5 hours after the final drug dose. Based on this interim analysis, the trial will accrue an additional 25 patients at this OTI.

Legal entity responsible for the study

Ivy Brain Tumor Center.

Funding

Ben and Catherine Ivy Foundation Barrow Neurological Foundation.

Disclosure

All authors have declared no conflicts of interest.

Background

Intracerebral (iCE) administration (admin) of ipilimumab (IPI) and nivolumab (NIVO) plus IV admin of NIVO following resection of rGB was well tolerated and resulted in encouraging overall survival (OS)(Schwarze et al, JITC 2021). In 4 subsequent cohorts (A to D), the safety of intratumoral (iTU) admin of NIVO and IPI, followed by repeated intracavitary (iCA), or intrathecal (iTH) admin of NIVO +/- increasing doses of IPI was investigated.

Methods

Within 24h prior to surgery, NIVO (10mg) was administered IV in all patients (pts), followed by a maximal safe resection (B+C), or biopsy (A+D), followed by iCE (B+C) or iTU (A+D) admin of IPI (5 mg) plus NIVO (10 mg). At the end of surgery, 10 mg NIVO plus 1, 5 or 10 mg of IPI was administered iCA or iTH (: Ommaya reservoir) in C and D respectively. iCA and iTH admin of NIVO with/-out IPI, as well as IV admin of NIVO (10 mg) were repeated Q2w (max 24w). On-treatment CSF samples were used for cytology, chemical analysis and measurements of NIVO/IPI concentrations.

Results

39 pts (27 male) were enrolled (A: n=16, B: n=16, C: n=4, D: n=3; enrolment ongoing in C+D). At database lock, all pts in A+B were off study treatment. All pts received the predefined dose of iCE/iTU IPI/NIVO. The median of iCE/IV NIVO admin was 5 (1-12) in A and 4(1-12) in B. Most frequent AEs were fatigue (n=30), headache (n=19), confusion (n=14), dysphasia (n=13), fever (n=10), and bacterial colonization of the Ommaya reservoir (n=5). On-treatment neurological deterioration due to subacute symptomatic cerebral edema requiring corticosteroids occurred in 6 pts. There were no G5 AEs. irAEs were infrequent. In A+B, PD was diagnosed in all pts, and 27 pts have died. Median PFS and OS were numerically inferior for pts treated in A vs. B (median PFS 5w (95% CI 1-8) vs. 13w (95% CI 7-19); median OS 23w (95% CI 0-53) vs. 42w (95% CI 30-54); 6m-OS-rate 50% (95% CI 26-75) vs. 68.8% (95% CI 46-91)). An elevated protein level and lymphocytic pleocytosis were observed in >90% of CSF samples. There was no evidence for accumulation of NIVO/IPI in the CSF.

Conclusions

Intracranial admin of NIVO +/- IPI in pts with rGB was found to be feasible, safe, and associated with encouraging OS in pts amenable to resection.

Clinical trial identification

NCT03233152.

Legal entity responsible for the study

Department of Medical Oncology, Universitair Ziekenhuis Brussel.

Funding

Has not received any funding.

Disclosure

B. Neyns: Financial Interests, Personal, Invited Speaker: Roche; Financial Interests, Personal, Invited Speaker: Bristol-Myers Squibb; Financial Interests, Personal, Invited Speaker: Merck Sharp & Dohme; Financial Interests, Personal, Invited Speaker: Novartis; Financial Interests, Personal, Invited Speaker: AstraZeneca; Financial Interests, Institutional, Funding: Pfizer; Financial Interests, Institutional, Funding: Novartis; Financial Interests, Institutional, Funding: Roche; Financial Interests, Institutional, Funding: Merck-Serono. J.K. Schwarze: Non-Financial Interests, Personal, Other: Amgen; Financial Interests, Personal, Invited Speaker: Novartis; Non-Financial Interests, Personal, Other: MSD Oncology. G. Awada: Financial Interests, Personal, Invited Speaker: Novartis; Financial Interests, Personal, Advisory Board: Novartis; Non-Financial Interests, Personal, Other: MSD Oncology; Non-Financial Interests, Personal, Other: Astellas Pharma; Non-Financial Interests, Personal, Other: Novartis; Non-Financial Interests, Personal, Other: Pfizer. All other authors have declared no conflicts of interest.