Focused Ultrasound for Blood-Brain Barrier Opening and Delivery of Anti-PD1 in Diffuse Midline Gliomas

PURPOSE/OBJECTIVE(S)

Diffuse midline glioma with H3K27 mutation is a fatal pediatric brain tumor, most commonly arising in the brainstem. This tumor remains universally fatal, despite a multitude of clinical trials, with a median overall survival of only 9-12 months. While immune-checkpoint inhibitors (ICIs) have transformed the treatment landscape of multiple solid tumors, delivery past the blood brain barrier (BBB) remains challenging. Programmed cell death protein 1 (PD1) is an immune checkpoint protein expressed on the surface of activated T cells; interaction with its ligand, PDL1, is tumor-protective, dampening T cell response. Recent phase I clinical trials have shown that ICIs targeting proteins along the PD1/PDL1 axis are well tolerated in patients with DMG; however, efficacy remains low. The blood-brain barrier (BBB) poses a major challenge to the efficacious delivery of therapeutic agents with large molecular size, such as anti-PD1. We hypothesize that BBB opening (BBBO) using focused ultrasound (FUS), a form of non-ionizing acoustic radiation, can enhance delivery and efficacy of anti-PD1 for treatment of DMG.

MATERIALS/METHODS

We established a syngeneic mouse DMG model with intracranial injection of cell line 4423 (PDGFB+, H3.3K27M, p53-/-). Magnetic resonance imaging (MRI) was utilized to evaluate BBBO and tumor progression. We measured delivery of anti-PD1 after BBBO using Western Blot and 3D in vivo optical fluorescent imaging/CT (OI/CT) of Cy7 labeled anti-PD1.

RESULTS

We demonstrate that delivery of anti-PD1 can be enhanced over 3.5-fold after reversible BBBO with FUS and concurrent microbubble administration. OI/CT revealed enhanced real-time antibody distribution peritumorally. Furthermore, we demonstrate that combined treatment of FUS and anti-PD1 led to benefit in local control of tumor growth using volumetric analysis of MRI. Preliminary survival studies suggest a positive trend for overall survival.

CONCLUSION

Our results support that FUS-mediated BBBO can increase treatment efficacy of anti-PD1 in a DMG murine model, due to improved targeted delivery to the tumoral region after systemic antibody administration. We consider these findings strong rationale for further investigation of the therapeutic effects of combinatorial treatment using FUS-mediated BBBO and ICIs for the treatment of DMG.

Minimally invasive surgical evacuation for spontaneous cerebellar hemorrhage: a case series and systematic review

Spontaneous cerebellar hemorrhage (scICH) is a subset of intracerebral hemorrhage accounting for 5-10% of all cases. Despite potential advantages, minimally invasive surgical evacuation of scICH may be an underutilized strategy when compared to unilateral or bilateral large suboccipital craniectomy or craniotomy, with or without duraplasty. We performed a retrospective single-center cohort study and a systematic literature review. Radiographic and clinical data were recorded and analyzed. Five consecutive patients with minimally invasive surgical evacuation of scICH were identified. Average hematoma size was 16.4 ± 3.0 cm3. Mean Glasgow coma score (GCS) prior to surgery was 11.6 ± 3.0 with improvement to 14.6 ± 0.4 postoperatively. Mean hematoma evacuation was 92.6 ± 0.6% as confirmed by postoperative computed tomography (CT) imaging. All patients achieved a modified Rankin Scale (mRS) score of 0 or 1 with an average follow-up time of 31 ± 22 months. Mean length of hospital stay was 8.8 ± 3.0 days. No patients experienced significant complications or required reoperation. Systematic review revealed similar results for minimally invasive evacuation of scICH when reporting disaggregated outcomes. A review of recent studies utilizing large unilateral or bilateral suboccipital craniectomy or craniotomy, with or without duraplasty, revealed higher morbidity and mortality rates than minimally invasive surgical evacuation of scICH. Minimally invasive evacuation of scICH is safe and effective. Near complete evacuation of hematoma can be achieved with lower morbidity and mortality than large suboccipital craniectomy or craniotomy. A multi-center, prospective, and rigorous trial comparing the two strategies for evacuation of scICH is warranted.

MODL-25. Radiation and focused ultrasound–mediated blood–brain barrier opening for DMG: safety and feasibility of combinatorial therapy

Diffuse midline glioma (DMG) is a pediatric tumor with dismal prognosis. Systemic therapeutic strategies have been unsuccessful to date and radiotherapy (RT) remains the standard of care. A central impediment to systemic therapy is the blood-brain barrier (BBB), which precludes drug delivery to the tumor site. Focused ultrasound (FUS) with intravenous microbubbles can transiently and non-invasively circumvent the BBB to enhance drug delivery. Nevertheless, it remains unclear whether FUS is safe at the brainstem in combination with clinical doses of RT. In this study, we hypothesized that FUS-mediated BBB-opening (BBBO) is safe and feasible with 39 Gy RT. To establish a safety timeline, we administered FUS to the brainstem of nontumor bearing mice concurrent with or adjuvant to radiation; then, we validated our findings in a syngeneic orthotopic xenograft DMG model which received repeated sonication concurrent with RT. Male B6 (Cg)-Tyrc-2J/J albino mice received intracranial injection of 4423 mouse DMG cells (PDGFB+, H3.3K27M, p53−/−) at a location posterior and lateral to the lambda. A clinical RT dose of 39 Gy in 13 fractions was delivered to the brainstem with the Small Animal Radiation Research Platform (SARRP) or the XRAD-320 irradiator. FUS was administered with a 0.5 MHz transducer, and both BBBO and tumor volume were monitored with MRI. FUS-mediated BBBO in nontumor bearing mice receiving RT did not affect cardiorespiratory rate, motor function, and tissue integrity. Moreover, tumor bearing mice tolerated repeated brainstem BBBO concurrent with RT. 39 Gy over 13 fractions offered local control, although disease progression occurred in all animals approximately 3-4 weeks post-RT. Ultimately, repeated FUS-mediated BBB opening concurrent with RT is safe and feasible. In our brainstem DMG model, relapse occurs, making it ideal for future tests of combinatorial RT and FUS-mediated drug delivery.

RADT-17. FOCUSED ULTRASOUND MEDIATED BLOOD–BRAIN BARRIER OPENING IS SAFE AND FEASIBLE CONCURRENT WITH AND ADJUVANT TO A CLINICAL RADIATION SCHEME FOR BRAINSTEM DMG

Diffuse midline gliomas (DMG) are pediatric tumors with dismal prognosis. When these tumors emerge in the brainstem, there exists no feasible method of surgical resection or systemic intervention, making ionizing radiation the sole therapeutic avenue to date. However, radiotherapy (RT) provides only marginal survival benefit as the topographically diffuse and highly infiltrative tumors spread in areas in which the blood-brain barrier (BBB) is relatively intact. Focused ultrasound (FUS) with intravenous microbubbles provides a compelling solution, transiently and non-invasively opening the BBB to allow drug delivery across the cerebrovasculature. Nonetheless, it remains unclear whether FUS can be safely administered at the brainstem in patients receiving RT. Therefore, the goal of this study was to assess the safety and feasibility of FUS administered concurrent with and adjuvant to a clinical hypofractionated radiation scheme for brainstem DMG. Non-tumor bearing B6 albino mice were randomly assorted into control, RT, FUS, and RT+FUS groups. Mice designated RT+FUS received 39Gy/13fx (hypofractionated RT scheme) to the brainstem with two sessions of FUS approximately 1 week apart. A single-element, spherical-segment FUS transducer driven by a function generator through a power amplifier was used with concomitant microbubble injection to sonicate the brainstem. Magnetic resonance imaging (MRI) was used to confirm BBB opening and cardiopulmonary measures were recorded throughout sonication. Vitals were assessed daily, and all treatment animals underwent Kondziela inverted screen testing and sequential weight lifting to assess brainstem-related strength and motor coordination deficits. In both FUS and RT+FUS mice, MRI confirmed brainstem BBB opening and subsequent closure within 96 hours. Mouse weights were stable, with slight drops (mean=5.5%) following FUS that resolved within three days. No attenuation in cardiorespiratory, strength, and motor coordination measurements was observed from FUS. FUS is a safe and feasible technique for brainstem BBB opening concurrent with and adjuvant to clinical hypofractionated RT.

EPCT-23 PRE-CLINICAL STUDY OF FOCUSED ULTRASOUND-MEDIATED BLOOD-BRAIN BARRIER OPENING AND PANOBINOSTAT FOR DIFFUSE INTRINSIC PONTINE GLIOMA TREATMENT

Diffuse intrinsic pontine glioma (DIPG) is the lethal high-grade brain tumor in children with no effective treatment options to date. Despite excessive clinical trials, the prognosis remains poor, with a median overall survival (mOS) of less than 1 year. Genomic studies of DIPG tissue have identified highly recurrent mutations in genes encoding histone H3 resulting in the substitution of lysine to methionine at position 27 (K27M), which is found in approximately 80% of DIPG. Recent drug screening studies identified the histone deacetylase (HDAC) inhibitors panobinostat as a highly effective drug against DIPG in vitro. However, due to the poor Blood-Brain Barrier (BBB) penetration of systemic administration, to enhance the delivery of panobinostat to improve treatment efficacy is needed. Focused ultrasound (FUS) has been shown to be able to safely and non-invasively open BBB to enhance drug delivery. Hence, in this study, we hypothesize that FUS-mediated BBBO (BBBO) can enhance the delivery of panobinostat for a therapeutic benefit in DIPG. Herein we established the syngeneic DIPG model by intracranially injecting mouse DIPG cells (PDGFB+, H3.3K27M, p53−/−) and used FUS and microbubbles to open BBB and enhance the panobinostat delivery. Magnetic resonance (MR) imaging was utilized to evaluate BBBO and tumor progression. We first demonstrated that FUS-mediated BBB-opening is safe and feasible to mice with DIPG tumors by MR imaging and passive cavitation detection. Moreover, this DIPG cell line is very sensitive to panobinostat in in vitro cytotoxicity assay. The combined treatment of FUS-mediated BBBO and panobinostat showed benefits in both local control and overall survival. The current results demonstrated FUS could increase the treatment efficacy of panobinostat to DIPG animals may be due to the increase of targeted delivery of systemic panobinostat to DIPG tumors in brainstem.

Hypercoagulable viscoelastic blood clot characteristics in critically ill coronavirus disease 2019 patients and associations with thrombotic complications

BACKGROUND

Critically ill coronavirus disease 2019 (COVID-19) patients have frequent thrombotic complications and laboratory evidence of hypercoagulability. The relationship of coagulation tests and thrombosis requires investigation to identify best diagnostic and treatment approaches. We assessed for hypercoagulable characteristics in critically ill COVID-19 patients using rotational thromboelastometry (ROTEM) and explored relationships of D-dimer and ROTEM measurements with thrombotic complications.

METHODS

Critically ill adult COVID-19 patients receiving ROTEM testing between March and April 2020 were analyzed. Patients receiving therapeutic anticoagulation before ROTEM were excluded. Rotational thromboelastometry measurements from COVID-19 patients were compared with non-COVID-19 patients matched by age, sex, and body mass index. Intergroup differences in ROTEM measurements were assessed using t tests. Correlations of D-dimer levels to ROTEM measurements were assessed in COVID-19 patients who had available concurrent testing. Intergroup differences of D-dimer and ROTEM measurements were explored in COVID-19 patients with and without thrombosis.

RESULTS

Of 30 COVID-19 patients receiving ROTEM, we identified hypercoagulability from elevated fibrinogen compared with non-COVID-19 patients (fibrinogen assay maximum clot firmness [MCF], 47 ± 13 mm vs. 20 ± 7 mm; mean intergroup difference, 27.4 mm; 95% confidence interval [CI], 22.1-32.7 mm; p < 0.0001). In our COVID-19 cohort, thrombotic complications were identified in 33%. In COVID-19 patients developing thrombotic complications, we identified higher D-dimer levels (17.5 ± 4.3 μg/mL vs. 8.0 ± 6.3 μg/mL; mean difference, 9.5 μg/mL; 95% CI, 13.9-5.1; p < 0.0001) but lower fibrinogen assay MCF (39.7 ± 10.8 mm vs. 50.1 ± 12.0 mm; mean difference, -11.2 mm; 95% CI, -2.1 to -20.2; p = 0.02) compared with patients without thrombosis. We identified negative correlations of D-dimer levels and ROTEM MCF in these patients (r = -0.61; p = 0.001).

CONCLUSION

We identified elevated D-dimer levels and hypercoagulable blood clot characteristics from increased fibrinogen on ROTEM testing in critically ill COVID-19 patients. However, we identified lower, albeit still hypercoagulable, ROTEM measurements of fibrinogen in COVID-19 patients with thrombotic complications compared with those without. Further work is required to externally validate these findings and to investigate the mechanistic drivers for these relationships to identify best diagnostic and treatment approaches for these patients.

LEVEL OF EVIDENCE

Epidemiologic, level IV.

Mortality and renal outcomes of patients with severe COVID-19 treated in a provisional intensive care unit

COVID-19 has created an enormous health crisis and this spring New York City had a severe outbreak that pushed health and critical care resources to the limit. A lack of adequate space for mechanically ventilated patients induced our hospital to convert operating rooms into critical care areas (OR-ICU). A large number of COVID-19 will develop acute kidney injury that requires renal replacement therapy (RRT). We included 116 patients with COVID-19 who required mechanical ventilation and were cared for in our OR-ICU. At 90 days and at discharge 35 patients died (30.2%). RRT was required by 45 of the 116 patients (38.8%) and 18 of these 45 patients (40%) compared to 17 with no RRT (23.9%, ns) died during hospitalization and after 90 days. Only two of the 27 patients who required RRT and survived required RRT at discharge and 90 days. When defining renal recovery as a discharge serum creatinine within 150% of baseline, 68 of 78 survivors showed renal recovery (87.2%). Survival was similar to previous reports of patients with severe COVID-19 for patients cared for in provisional ICUs compared to standard ICUs. Most patients with severe COVID-19 and AKI are likely to recover full renal function.

Functional Coagulation Differences Between Lobar and Deep Intracerebral Hemorrhage Detected by Rotational Thromboelastometry: A Pilot Study

BACKGROUND

Lobar intracerebral hemorrhage (ICH) is known to have better clinical outcomes and preliminary evidence of less hematoma expansion compared to deep ICH. No functional coagulation differences between lobar and deep ICH have been identified using traditional plasma-based coagulation tests. We investigated for coagulation differences between lobar and deep ICH using whole-blood coagulation testing (Rotational Thromboelastometry: [ROTEM]).

METHODS

Clinical, radiographic, and laboratory data were prospectively collected for primary ICH patients enrolled in a single-center ICH study. Patients with preceding anticoagulant use or admission coagulopathy on traditional laboratory testing were excluded. Lobar and deep ICH patients receiving admission ROTEM were analyzed. Linear regression was used to assess the association of ICH location with coagulation test results after adjusting for potential confounders.

RESULTS

There were 12 lobar and 19 deep ICH patients meeting inclusion criteria. Lobar ICH patients were significantly older and predominantly female. Lobar ICH had faster intrinsic pathway coagulation times (139.8 vs 203.2 s; 95% CI - 179.91 to - 45.96; p = 0.002) on ROTEM testing compared to deep ICH after adjusting for age, sex, and hematoma volume. This revealed functional coagulation differences, specifically quicker clot formation in lobar compared to deep ICH. No differences were noted using traditional coagulation testing (prothrombin time/partial thromboplastin time/platelet count).

CONCLUSIONS

Our pilot data may suggest that there are functional coagulation differences between lobar and deep ICH identified using ROTEM. Whole-blood coagulation testing may be useful in assessing coagulopathy in ICH patients and in determining reversal treatment paradigms, though further work is needed.

A phase II randomized controlled trial of tiopronin for aneurysmal subarachnoid hemorrhage

OBJECTIVE

Delayed cerebral ischemia (DCI) is a significant contributor to poor outcomes after aneurysmal subarachnoid hemorrhage (aSAH). The neurotoxin 3-aminopropanal (3-AP) is upregulated in cerebral ischemia. This phase II clinical trial evaluated the efficacy of tiopronin in reducing CSF 3-AP levels in patients with aSAH.

METHODS

In this prospective, randomized, double-blind, placebo-controlled, multicenter clinical trial, 60 patients were assigned to receive tiopronin or placebo in a 1:1 ratio. Treatment was commenced within 96 hours after aSAH onset, administered at a dose of 3 g daily, and continued until 14 days after aSAH or hospital discharge, whichever occurred earlier. The primary efficacy outcome was the CSF 3-AP level at 7 ± 1 days after aSAH.

RESULTS

Of the 60 enrolled patients, 29 (97%) and 27 (93%) in the tiopronin and placebo arms, respectively, received more than one dose of the study drug or placebo. At post-aSAH day 7 ± 1, CSF samples were available in 41% (n = 12/29) and 48% (n = 13/27) of patients in the tiopronin and placebo arms, respectively. No difference in CSF 3-AP levels at post-aSAH day 7 ± 1 was observed between the study arms (11 ± 12 nmol/mL vs 13 ± 18 nmol/mL; p = 0.766). Prespecified adverse events led to early treatment cessation for 4 patients in the tiopronin arm and 2 in the placebo arm.

CONCLUSIONS

The power of this study was affected by missing data. Therefore, the authors could not establish or refute an effect of tiopronin on CSF 3-AP levels. Additional observational studies investigating the role of 3-AP as a biomarker for DCI may be warranted prior to its use as a molecular target in future clinical trials.Clinical trial registration no.: NCT01095731 (ClinicalTrials.gov).

Abstract 150: A Phase II Multicenter Randomized Controlled Trial of Tiopronin for Aneurysmal Subarachnoid Hemorrhage

Introduction: Subacute symptomatic neurological decline is a significant and preventable contributor to patient morbidity and mortality after aneurysmal subarachnoid hemorrhage (aSAH). 3-Aminopropanal (3-AP) is a potent neurotoxin that is upregulated in the setting of cerebral ischemia. Targeted neutralization has achieved a neuroprotective effect in preclinical models. This phase II trial evaluated the efficacy of Tiopronin administration in reducing 3-AP levels in patients with aSAH.

Methods: We designed a prospective, randomized, double-blind, placebo-controlled clinical trial that was conducted in three centers in the United States. 60 patients were enrolled and assigned to receive Tiopronin or placebo in a 1:1 ratio from enrolment until the earlier to occur of post-bleed day 14 or hospital discharge. Patients received a total of 3 grams daily, in 3 divided doses. The primary efficacy endpoint was the change in serum and/or cerebrospinal fluid (CSF) 3-AP from enrolment to study drug discontinuation.

Results: Of the 60 enrolled patients, 29 (97%) in the treatment arm and 27 (93%) in the control arm received more than one dose of the study drug. A greater relative reduction in serum 3-AP level was observed in the treatment arm (adj Beta=-0.689, 95% C.I.=-2.730, -0.008; p=0.049). This was most apparent, but did not reach significance, in patients with grade IV-V aSAH (adj Beta=-0.808; 95% C.I.=-3.872, 0.167; p=0.067). No difference in the change in CSF level was observed (adj Beta=0.048, 95% C.I.=-2.334, 2.589; p=0.903). Pre-specified adverse events led to early cessation of treatment for four patients in the treatment arm, and two in the control arm.

Conclusion: Tiopronin attenuated the accumulation of serum 3-AP, providing the first translational evidence for the use of 3-AP antagonists in aSAH. Further investigation to evaluate for a dose-response relationship in Tiopronin’s ability to cross the blood-brain barrier is recommended. <!--EndFragment-->