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Abstract B028: Systemic and CNS distributional pharmacokinetics of WSD0628, a novel radiosensitizer: Implications for the treatment of brain tumors
Xue, Zhiyi , Oh, Ju‐Hee , Le, Jiayan, Sarkaria, Jann S., Elmquist, William F. , Rathi, Sneha , Mladek, Ann C. , Xue, Zhiyi, Zhang, Wenjuan , Zhang, Wenqiu

Mayo Clinic

Cancer Research | March 4, 2024 | Volume: 84 | Issue: 5_Supplement_1 | Pages: B028-B028

10.1158/1538-7445.brain23-b028 Get It

Abstract Glioblastoma (GBM) is an aggressive and highly infiltrative brain tumor with poor prognosis. Radiation therapy induces DNA damage, and DNA damage response (DDR) pathways modulate resistance to radiation therapy. Inhibiting DDR pathways by targeting ATM, a key enzyme involved in the repair of DNA double strand breaks, leads to radiosensitization and enhances cytotoxicity. Clinical translation of radiosensitizers for GBM may be influenced by a lack of effective drug delivery across the blood brain barrier (BBB). The purpose of this study is to determine the key preclinical pharmacokinetic parameters and mechanisms that influence the CNS delivery of WSD0628, a novel ATM inhibitor. In vitro clonogenic survival assays using U251 GBM cells indicate that WSD0628 shows significant radiosensitization, with a >70% decrease in surviving colonies in the presence of 10nM or higher drug concentrations in combination with 2.5 to 10 Gy radiation as compared to radiation alone. We evaluated the systemic pharmacokinetics and CNS distribution of WSD0628 in FVB wild-type mice and FVB mice lacking Pgp and Bcrp (Mdr1a/b−/−Bcrp1−/−, triple knockout) after a 1, 5, 10 mg/kg intravenous (IV) or oral (PO) dose. Clearance decreased with increase in dose and a greater than dose proportional increase in exposure was observed. WSD0628 is rapidly absorbed and is bioavailable after oral administration. Tissue distribution coefficients were determined as the ratio of exposure in tissue to plasma (Kp = AUCtissue/AUCplasma). Kp,brain was 0.22 ± 0.05, and Kp, spinal cord was 0.30 ± 0.09 in the wild-type mice. For wild-type mice, Kp,uu,brain was 0.20 ± 0.05 and Kp,uu,spinal cord was 0.26 ± 0.08, determined by correcting for binding to CNS tissues and plasma. The brain distribution of WSD0628 was only modestly increased (1.4 times) in the triple knockout mice with Kp,brain of 0.32 ± 0.06 and Kp,spinal cord of 0.41 ± 0.08. Organ distribution of WSD0628 at steady-state was studied after intraperitoneal implantation of Alzet osmotic pumps primed to release WSD0628 at 7.5 ug/hr for 25 hours. Tissue distribution coefficients, determined by organ-to-plasma steady-state concentration ratios, were highest for liver and kidneys, followed by heart, lungs and CNS. Survival studies conducted in mice bearing orthotopic GBM patient derived xenografts show a significant improvement in survival in mice receiving a combination of WSD0628 and radiation as compared to radiation alone. In conclusion, WSD0628 is a robust radiosensitizer and has moderate brain penetration that is not limited by the efflux transporters Pgp and Bcrp. Based on preliminary efficacy studies in mice, WSD0628 shows potential for treatment of GBM tumors. Evaluations are underway to determine tumor free concentrations and quantification of corresponding biomarkers. Combining this knowledge of PK of WSD0628 with the dynamics of the targeted biological pathway will inform a PK-PD-efficacy model and predict effective dosage regimens for future preclinical and clinical trials. Citation Format: Sneha Rathi, Ann Mladek, Zhiyi Xue, Ju-Hee Oh, Wenjuan Zhang, Wenqiu Zhang, Jiayan Le, Jann S. Sarkaria, William F. Elmquist. Systemic and CNS distributional pharmacokinetics of WSD0628, a novel radiosensitizer: Implications for the treatment of brain tumors [abstract]. In: Proceedings of the AACR Special Conference on Brain Cancer; 2023 Oct 19-22; Minneapolis, Minnesota. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_1):Abstract nr B028.
Abstract B023: CNS and systemic pharmacokinetics of antibody-drug conjugate payloads through convection-enhanced delivery
Griffith, Jessica I. , Le, Jiayan, Porath, Kendra A. , Elmquist, William F. , Jain, Sonia , Bakken, Katrina K. , Sarkaria, Jann N.

Mayo Clinic

Cancer Research | March 4, 2024 | Volume: 84 | Issue: 5_Supplement_1 | Pages: B023-B023

10.1158/1538-7445.brain23-b023 Get It

Abstract Glioblastoma (GBM) is one of the most malignant central nervous system (CNS) tumors and accounts for more than 60% of primary brain tumors in adults [1]. While chemotherapy is a frequently employed treatment for GBM, its lack of specificity towards tumor cells leads to toxicity in healthy tissues. Antibody-drug conjugates (ADCs) are a prevalent targeted-drug delivery strategy that may enhance the therapeutic window. ADC development for GBM has progressed in recent years, yet recent clinical trials have thus far failed to demonstrate drug efficacy [2]. This is likely attributed to poor brain penetration and heterogeneous drug distribution within GBM [3]. Convection-enhanced delivery (CED) is an invasive delivery method that can achieve direct administration of therapeutics to brain tumors and potentially could be used to enhance the delivery and efficacy of ADCs. This study investigates the CNS and systemic pharmacokinetics and distribution of similar payload molecules following CED administration of two GBM-targeting ADCs, ABBV-221 and ABT-414. The ADC payloads are monomethyl auristatin E (MMAE) and monomethyl auristatin F (MMAF), respectively, and both are potent anti-tubulin toxins commonly used as warheads for ADCs. Both ADCs and free MMAE were administered as single doses to FVB mice via CED infusion or intraperitoneal (IP) injection. Plasma and brain samples were collected over 24 hours for ABBV-221 and 96 hours for ABT-414, and unconjugated payload molecules were quantified via LC-MS/MS analysis. The results showed that free (i.e., not bound to the targeting antibody) MMAE has a significantly higher exposure in brain compared to plasma when delivered via CED, and exposure in the right hemisphere was 10-fold higher than the left hemisphere, as the site of CED infusion was located in the right hemisphere for all trials. Similar results for MMAE payload were observed after the CED of ABBV-221. Systemic administration of ABBV-221 resulted in a nearly 100-fold decrease in unconjugated MMAE concentration in brain, indicating the poor brain penetration of the ADC. Similarly, following the CED of ABT-414, unconjugated payload concentration was the highest in right anterior brain among all brain regions, and plasma concentration was below the limit of quantification. Systemic injection of ABT-414 resulted in non-quantifiable payload concentrations in either brain or plasma samples. Taking these results as a whole, this study demonstrated significantly enhanced brain distribution of payload molecules from GBM-targeting ADCs following CED compared to systemic administration. The consistent payload delivery pattern observed in both ADCs further supports the potential of CED as an effective drug delivery method for the treatment of GBM. These findings highlight the promise of CED as a means to address the limitations of conventional chemotherapy and improve therapeutic outcomes in GBM treatment. 1. Sarkaria JN et al. Neuro Oncol. 2018; 20:184–91. 2. Lassman AB et al. Neuro Oncol. 2023; 25:339–50. 3. Marin B-M, et al. Neuro Oncol. 2021; 23:2042–53. Citation Format: Jessica I. Griffith, Jiayan Le, Kendra A. Porath, Sonia Jain, Katrina K. Bakken, Jann N. Sarkaria, William F. Elmquist. CNS and systemic pharmacokinetics of antibody-drug conjugate payloads through convection-enhanced delivery [abstract]. In: Proceedings of the AACR Special Conference on Brain Cancer; 2023 Oct 19-22; Minneapolis, Minnesota. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_1):Abstract nr B023.
Abstract B009: Characterizing the super enhancer landscape of H3K27me3 loss in MPNST and DIPG
Bhunia, Minu , Caride, Ariel J. , Ördög, Tamás , Largaespada, David A. , Stehn, Christopher M. , Williams, Kyle , Larsson, Alex T. , Lee, Jeong‐Heon , Largaespada, David A.

Mayo Clinic

Cancer Research | March 4, 2024 | Volume: 84 | Issue: 5_Supplement_1 | Pages: B009-B009

10.1158/1538-7445.brain23-b009 Get It

Abstract Neurofibromatosis type 1 (NF1) syndrome is an autosomal dominant cancer predisposition syndrome defined by germline deletion of one NF1 allele. Somatic loss of heterozygosity in the remaining NF1 allele in Schwann lineage cells gives rise to benign tumors known as plexiform neurofibromas. These tumors have a high risk of transforming into malignant peripheral nerve sheath tumors (MPNST) through the sequential deletion of CDKN2A/B followed by recurrent mutations in SUZ12 or EED, constituting the inactivation of polycomb repressor complex 2 (PRC2). PRC2 is a transcriptional repressor complex involved in the silencing of several development and differentiation genes. Loss of this complex leads to a depletion in trimethylation marks on Histone H3 Lysine 27 (H3K27me3) and the subsequent gain of acetylation marks on the same lysine residue (H3K27Ac). These molecular hallmarks are shared with diffuse intrinsic pontine gliomas (DIPG) harboring the H3K27M mutation which prevents effective deposition of H3K27me3, thus having similar molecular phenotypes to MPNST. However, the full range of epigenetic consequences of these events are currently not well characterized. Additionally, given that MPNSTs originate from cells of neural crest origin and DIPGs from cells of neural origin, it is not know to what degree epigenetic changes stemming from H3K27me3-loss are general across tumors or are context-dependent based on cell-of-origin. In order to contribute to this effort, the Largaespada lab has engineered Schwann cell lines to harbor deletions in NF1 and either SUZ12 or EED and assayed the H3K27ac landscape of these cells in addition to patient-derived MPNST cell lines. Utilizing the ranked ordering of super enhancers (ROSE) algorithm, we have identified common super enhancers within each MPNST cell line. These super enhancer elements are located nearby a variety of putative oncogenes responsible for the maintenance of cell identity. These elements were then compared to publicly available data from DIPG primary and patient-derived samples to understand common regulatory events driven by loss of H3K27me3 as well as molecular signatures present only in MPNST or in DIPG that may be a result of PRC2 or H3K27M alone. We further characterized these super enhancers by assessing the expression levels of their associated genes to understand their role in transcriptional activation. These efforts provide a roadmap of the super enhancer landscape of both MPNSTs and DIPGs to investigate novel mechanisms of H3K27me3-dependent tumorigenesis while also contributing to knowledge of potential effects of H3K27me3-loss that dependent on the cell-of-origin for each respective tumor. Citation Format: Christopher M. Stehn, Minu Bhunia, Kyle Williams, Alex T. Larsson, Ariel Caride, Jeong-Heon Lee, Tamas Ordog, David Largaespada. Characterizing the super enhancer landscape of H3K27me3 loss in MPNST and DIPG [abstract]. In: Proceedings of the AACR Special Conference on Brain Cancer; 2023 Oct 19-22; Minneapolis, Minnesota. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_1):Abstract nr B009.
Abstract B025: How much is enough? BI-907828: a MDM2-p53 antagonist with limited BBB penetration but potent efficacy in glioblastoma
Oh, Ju‐Hee , Mlade, Ann, Elmquist, William F. , Zhang, Wenjuan , Vaubel, Rachael A. , Talele, Surabhi , Zhang, Wenqiu , Waller, Katie L. , Burgenske, Danielle M. , Sarkaria, Jann N.

Mayo Clinic

Cancer Research | March 4, 2024 | Volume: 84 | Issue: 5_Supplement_1 | Pages: B025-B025

10.1158/1538-7445.brain23-b025 Get It

Abstract Glioblastoma (GBM) is a highly aggressive and infiltrative primary malignant brain tumor. Current standard-of-care for newly diagnosed GBM patients includes maximal safe surgical resection, followed by concurrent radiation with temozolomide (TMZ), and adjuvant TMZ chemotherapy. However, despite aggressive treatments, GBM patients have a poor prognosis, with a median survival of 14.6 months and a 5-year survival rate of 6.8%. The p53 protein is a critical tumor suppressor in the cell cycle. The expression level of p53 is tightly controlled by its negative regulator, murine double minute 2 (MDM2). Amplification of the MDM2 gene, found in 14 % of GBMs, can inactivate p53, leading to loss of tumor suppressor functions. Therefore, we are investigating a potent MDM2 antagonist – BI-907828 in GBM to restore the p53 tumor suppressor function by inhibiting the p53/MDM2 interactions. We aim to evaluate the PK/PD of BI-907828 and demonstrate a new translational paradigm to rethink the “Delivery – Potency – Efficacy” relationship in drug discovery and development for central nervous system (CNS) tumors. BI-907828 was evaluated for cytotoxicity and the inhibition effect to MDM2-p53 pathway. Systemic PK and transport mechanisms controlling CNS distribution were evaluated in wild-type and transgenic mice that lack of efflux transporters P-gp and BCRP. BI-907828 unbound fractions in cell media, mouse and human specimens were determined by using rapid equilibrium dialysis to evaluate “active” concentrations. Efficacy measures, including survival and free drug distribution in tumor were assessed in mouse orthotopic GBM xenografts. BI-907828 exhibited potent inhibition of MDM2-p53 pathway and promoted cell death in GBM TP53 wild-type cells. MDM2-amplified cells are highly sensitive to BI-907828, with an effective unbound concentration of 0.1 nM. The CNS distribution of BI-907828 is limited by BBB efflux mediated by P-gp, resulting in a brain free partition coefficient Kp,uu of 0.002. Despite this seemingly “poor” BBB penetration, weekly administration of 10 mg/kg BI-907828 significantly extended median survival of orthotopic GBM108 xenografts to 218 days compared to 28 days with vehicle treatment (P < 0.0001). These studies show that efficacy of BI-907828 in orthotopic models is related to high potency even though its CNS distribution is severely limited by BBB efflux. In another words, in this case, this little drug distribution to brain is “enough” for extending survival of orthotopic GBM108 xenografts. Therefore, a comprehensive understanding of drug “Delivery – Potency – Efficacy” relationship is warranted in drug discovery development, especially for treatment of CNS tumors. Citation Format: Wenjuan Zhang, Rachael Vaubel, Juhee Oh, Ann Mlade, Surabhi Talele, Wenqiu Zhang, Katie Waller, Danielle Burgenske, Jann Sarkaria, William Elmquist. How much is enough? BI-907828: a MDM2-p53 antagonist with limited BBB penetration but potent efficacy in glioblastoma [abstract]. In: Proceedings of the AACR Special Conference on Brain Cancer; 2023 Oct 19-22; Minneapolis, Minnesota. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_1):Abstract nr B025.
Prevalence and patterns of laxative use in subjects with self-reported constipation: results from a multinational digestive health survey
Lacy, Brian E. , Delfini, Régis, Fladung, Bernward, Delfini, Regis, Lange, Robert

Mayo Clinic

Therapeutic Advances in Gastroenterology | March 4, 2024 | Volume: 17 | Issue: No issue available | Pages: No page available

10.1177/17562848241232605 | PMID 38445248 Get It

Background: Constipation is characterized by symptoms of straining, hard stool, difficult evacuation, and infrequent bowel movements. Online surveys provide valuable information about patients’ perspectives, symptoms, management, treatment satisfaction, and risk factors. Methods: This survey explored subject experiences involving 20 gastrointestinal (GI) conditions. In total, 20,099 respondents in seven countries with varied cultural and socioeconomic backgrounds participated. Post hoc analysis of ‘self-reported constipation’ and related symptoms experienced within the past 6 months and the last episode of constipation provided data on prevalence, demographics, frequency and duration of episodes and related symptoms, impact on quality of life (QoL), management with or without laxatives, and resulting treatment satisfaction. Results: In total, 10,425 subjects reported constipation within 6 months and 2637 at the last episode. Prevalence was highest in females and younger adults. Most subjects reported various coexisting GI symptoms. Almost 80% of 6865 episodes reported by 5337 subjects occurred every 2–3 months to every 2–3 weeks. A higher frequency of constipation correlated with a greater impact on QoL. On a 10-point scale, the mean impact was 6.4. More than 90% of respondents had episodes ranging from 1 day to 1 week. More than 90% took action; 16% used laxatives, of whom 80.3% were satisfied. Conclusion: Constipation, a highly prevalent disorder, spans cultures and socioeconomic classes. Its chronic recurrence has a significant impact on QoL, resulting in symptom self-management in >90% of subjects. Significantly higher satisfaction rates in subjects treated with than without laxatives reflect subjects’ reports that self-reported constipation can be treated effectively with laxatives.
Examining the Role of Cerebral Embolic Protection Devices in Preventing Postoperative Stroke in Patients with a History of Stroke or Transient Ischemic: Insights from the National Inpatient Sample
Mondal, Avilash , Pingili, Adhvithi , Nayak, Parth R., Patel, Harshil , Qaqish, Omar, Vyas, Ankit , Kondur, Ashok , Katukuri, Nishanth , Desai, Rupak , Borra, Vamsikalyan , Jain, Akhil

Mayo Clinic

Cardiology in Review | March 4, 2024 | Volume: 34 | Issue: 2 | Pages: 134-137

10.1097/crd.0000000000000674 | PMID 38436403 Get It

Cerebral embolic protection devices (CEPD) during transcatheter aortic valve replacement (TAVR) have been shown to lower the risk of stroke during the procedure. However, their long-term and clinical effects on neuro-cognition are unknown. Therefore, we hypothesized the benefit of CEPD in TAVR patients with a prior history of stroke or transient ischemic attack (TIA). National Inpatient Sample (2019) and International Classification of Diseases, 10th Revision codes were used to identify patients undergoing TAVR with prior stroke or TIA. Propensity-matched analysis was performed to adjust for baseline characteristics and comorbidities. Primary outcome measures were postoperative stroke and all-cause mortality. Length of stay and hospital cost were secondary outcomes. Of 8450 unmatched TAVR patients with prior stroke or TIA in 2019, 1095 (13%) utilized CEPD. After propensity matching previous myocardial infarction (MI), coronary artery bypass grafting, and drug abuse were higher in the TAVR-only cohort. Postoperative stroke rate (1.4% vs 2.2%; P = 0.081) and odds [adjusted odds ratio (aOR), 0.48; 95% confidence interval (CI), 0.11–2.17; P = 0.341] were lower in the CEPD group. There was no difference in all-cause in-hospital mortality between the 2 groups (0.9% vs 1.0%). Length of stay (3 vs 2 days, P <0.001) and hospital expenditure ($172,711 vs $162,284; P = 0.002) were higher for the TAVR-only cohort. CEPD in TAVR patients with prior stroke or TIA did not show statistically significant postoperative stroke benefits. However, further larger-scale prospective studies are needed to evaluate the long-term neurocognitive benefits of CEPD in these patients. As the use of TAVR continues to expand, optimizing peri-procedural strategies such as the use of CEPD remains a critical area of research to improve patient outcomes.
Patient Characteristics and the Extent to Which Clinicians Involve Patients in Decision Making: Secondary Analyses of Pooled Data
Keij, Sascha M. , Montori, Víctor M. , Brito, Juan P. , Kunneman, Marleen , Pieterse, Arwen H. , Branda, Megan E. , Montori, Victor M , Kunneman, Marleen , Pieterse, Arwen H , Brito, Juan P

Mayo Clinic

Medical Decision Making | March 4, 2024 | Volume: 44 | Issue: 3 | Pages: 346-356

10.1177/0272989x241231721 | PMID 38563311 Get It

Background The occurrence of shared decision making (SDM) in daily practice remains limited. Various patient characteristics have been suggested to potentially influence the extent to which clinicians involve patients in SDM. Objective To assess associations between patient characteristics and the extent to which clinicians involve patients in SDM. Methods We conducted a secondary analysis of data pooled from 10 studies comparing the care of adult patients with (intervention) or without (control) a within-encounter SDM conversation tool. We included studies with audio(-visual) recordings of clinical encounters in which decisions about starting or reconsidering treatment were discussed. Main Measures In the original studies, the Observing Patient Involvement in Decision Making 12-items (OPTION 12 item ) scale was used to code the extent to which clinicians involved patients in SDM in clinical encounters. We conducted multivariable analyses with patient characteristics (age, gender, race, education, marital status, number of daily medications, general health status, health literacy) as independent variables and OPTION 12 as a dependent variable. Results We included data from 1,614 patients. The between-arm difference in OPTION 12 scores was 7.7 of 100 points ( P < 0.001). We found no association between any patient characteristics and the OPTION 12 score except for education level ( p = 0.030), an association that was very small (2.8 points between the least and most educated), contributed mostly by, and only significant in, control arms (6.5 points). Subanalyses of a stroke prevention trial showed a positive association between age and OPTION 12 score ( P = 0.033). Conclusions Most characteristics showed no association with the extent to which clinicians involved patients in SDM. Without an SDM conversation tool, clinicians devoted more efforts to involve patients with higher education, a difference not observed when the tool was used. Highlights Most sociodemographic patient characteristics show no association with the extent to which clinicians involve patients in shared decision making. Clinicians devoted less effort to involve patients with lower education, a difference that was not observed when a shared decision-making conversation tool was used. SDM conversation tools can be useful for clinicians to better involve patients and ensure patients get involved equally regardless of educational background.
Abstract B033: Histone H3.3 K27M and G34R/V glioma driver mutations inhibit mitotic phosphorylation of H3.3 S31, driving tumor formation by inducing chromosomal instability
Grigore, Florina , Langfald, Alyssa, Hakkim, Faruck Lukmanul , Vaughan, Kevin T. , Day, Charles , Daniels, David J. , Robinson, James, Hinchcliffe, Edward H.

Mayo Clinic

Cancer Research | March 4, 2024 | Volume: 84 | Issue: 5_Supplement_1 | Pages: B033-B033

10.1158/1538-7445.brain23-b033 Get It

Abstract Diffuse gliomas are pediatric high-grade gliomas that frequently harbor heterozygous histone H3.3 K27M, G34R, or G34V mutations. These mutations alter histone methylations, although the precise mechanism(s) of gliomagenesis remains uncertain. H3.3 contains a unique Serine at position 31 that is phosphorylated in prophase and dephosphorylated in anaphase during normal cell division. Previously we have reported that chromosome missegregation triggers H3.3 S31 phosphorylation along chromosome arms in ana/telophase leading to p53-induced cell cycle arrest. Here we show, in vitro and in vivo, that H3.3 K27M, G34R, and G34V suppress S31 phosphorylation by its mitotic kinase, Chk1. In diploid cells, overexpression of H3.3 K27M, G34R, G34V, or non-phosphorylatable S31A significantly increases the frequency of chromosome missegregation, while H3.3 K36M did not. This missegregation phenotype could be rescued by overexpression of K27M/S31E or G34R/S31E double mutants. Next, we used CRISPR/Cas9 gene editing to revert K27M or G34V patient-derived DMG cells to WT or replace the mutant allele with S31A. Reversion to WT increased metaphase S31 phosphorylation and reduced chromosome missegregations, but inserting an S31A mutation caused more mitotic defects. Following a mitotic error, newly formed aneuploid cells overexpressing K27M, G34R, or G34V suppress p53 levels and continue to divide, while WT overexpressing cells always arrest. To test the effects of diminished S31 phosphorylation on gliomagenesis, we utilized a novel mouse model of glioma. Expression of PDGFß linked to H3.3K27M, H3.3G34R, and H3.3S31A in neural stem cells in vivo promoted the development of high-grade gliomas in under 100 days, whereas PDFß-H3.3WT did not. Notably, the S31A tumors had histologically normal levels of K27me3 and K36me3. This work shows that a single glioma-associated point mutation in H3.3 can generate chromosomal instability, and which is a major contributing factor to H3.3 K27M and G34-altered glioma formation. Citation Format: Charles A. Day, Florina Grigore, Alyssa Langfald, Faruck Hakkim, David Daniels, Kevin Vaughan, James Robinson, Edward Hinchcliffe. Histone H3.3 K27M and G34R/V glioma driver mutations inhibit mitotic phosphorylation of H3.3 S31, driving tumor formation by inducing chromosomal instability [abstract]. In: Proceedings of the AACR Special Conference on Brain Cancer; 2023 Oct 19-22; Minneapolis, Minnesota. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_1):Abstract nr B033.
Abstract A033: Murine CNS and bone marrow distribution of the aurora A kinase inhibitor alisertib: Pharmacokinetics and exposure at the sites of efficacy and toxicity
Oh, Ju‐Hee , Elmquist, William F. , Power, Erica A. , Zhang, Wenjuan , Daniels, David J.

Mayo Clinic

Cancer Research | March 4, 2024 | Volume: 84 | Issue: 5_Supplement_1 | Pages: A033-A033

10.1158/1538-7445.brain23-a033 Get It

Abstract Important challenges in developing drugs that target central nervous system (CNS) tumors include overcoming barriers for CNS delivery and reducing systemic side effects. Alisertib, an aurora A kinase inhibitor, has been examined for treatment of several CNS tumors in preclinical and clinical studies. In this study, we investigated the distribution of alisertib into the CNS, the site of efficacy for brain tumors, and into the bone marrow, the site of dose-limiting toxicity leading to myelosuppression. Mechanisms influencing site-specific distribution, such as active transport mediated by the efflux proteins, p-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp), were examined. Alisertib exposure to the brain in wild-type mice was less than 1% of that in the plasma and was evenly distributed throughout various brain regions and the spinal cord. Studies using transporter knockout mice and pharmacological inhibition show that alisertib CNS distribution is influenced by P-gp, but not Bcrp. Conversely, upon systemic administration, alisertib distribution to the bone marrow occurred rapidly, was not significantly limited by efflux transporters, and reached higher concentrations than in the CNS. This study demonstrates that, given an equivalent distributional driving force exposure in plasma, the exposure of alisertib in the brain is significantly less than that in the bone marrow, suggesting that targeted delivery may be necessary to guarantee therapeutic efficacy with minimal risk for adverse events. Therefore, these data suggest that, to improve the therapeutic index when using alisertib for brain tumors, a localized regional delivery, such as convection-enhanced delivery, may be warranted. Citation Format: Juhee Oh, Erica A. Power, Wenjuan Zhang, David J. Daniels, William F. Elmquist. Murine CNS and bone marrow distribution of the aurora A kinase inhibitor alisertib: Pharmacokinetics and exposure at the sites of efficacy and toxicity [abstract]. In: Proceedings of the AACR Special Conference on Brain Cancer; 2023 Oct 19-22; Minneapolis, Minnesota. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_1):Abstract nr A033.
Abstract A004: GTP signaling links metabolism, DNA repair, and responses to genotoxic stress
Zhou, Weihua , Zhao, Zitong , Lin, Angelica , Xu, Jie , Wilder-Romans, Kari , Yang, Annabel , Solanki, Sumeet , Yao, Yangyang , Peterson, Erik , Korimerla, Navyateja , Werner, Christian K. , Liang, Jessica , Jacobson, Janna , O'Brien, Alexandra, Elaimy, Ameer L. , Ferris, Sean P. , Zhao, Shuang G. , Zhang, Shuqun , Morgan, Meredith A. , Lawrence, Theodore S. , Lyssiotis, Costas A. , Peters‐Golden, Marc , Wahl, Daniel , Lawrence, Theodore S , Lyssiotis, Costas A , Yang, John, Scott, Andrew J. , Li, Jing , Speth, Jennifer M. , Walker, Natalie , Kothari, Ayesha U. , Palavalasa, Sravya , Zhao, Shuang G , Sarkaria, Jann N. , Győrffy, Balázs , Al‐Holou, Wajd N. , Umemura, Yoshie , Shah, Yatrik M

Mayo Clinic

Cancer Research | March 4, 2024 | Volume: 84 | Issue: 5_Supplement_1 | Pages: A004-A004

10.1158/1538-7445.brain23-a004 Get It

Abstract OBJECTIVE: We sought to define the mechanisms by which purines regulate DNA repair and therapy response. METHODS: Phosphoproteomics was used to identify GTP-dependent (de)phosphorylation events after radiation (RT) and antibodies generated against novel sites. Animal models of glioblastoma (GBM) and normal tissues were used to assess DNA repair and treatment responses in vivo. RESULTS: Pharmacogenomic inhibition of GTP (but not ATP) synthesis sensitized GBM cells to RT by inhibiting the activity of non-homologous end joining, but not homologous recombination. We found a GTP-dependent RT-induced dephosphorylation event on Abl interactor 1 (Abi-1) serine 323 (S323) using phosphoproteomics. We generated a new antibody for p-Abi-1 (S323), validated its specificity, and confirmed that RT causes a GTP-dependent dephosphorylation of Abi-1 (S323). Knockout of Abi-1 slowed RT-induced double-strand break (DSB) repair, and this was rescued by re-expression of dephosphomimetic Abi-1 (S323A) but not phosphomimetic Abi-1 (S323D). Abi-1 canonically binds to G protein Rac1. Expression of constitutively active Rac1 promoted but dominant negative Rac1 blocked the dephosphorylation of Abi-1 (S323) and DSB repair. Knock-down or inhibition of protein phosphatase 5 reversed the GTP- and Rac1-mediated dephosphorylation of Abi-1 and DSB repair. In GBM PDX samples, p-Abi-1 (S323) levels negatively correlated with Rac1 activity and predicted favorable efficacy of genotoxic treatments. In orthotopic GBM mouse models, inhibiting Rac1 enhanced RT responses and suppressed Abi-1 (S323) dephosphorylation. Abi-1 knockout enhanced efficacy of genotoxic treatments and could be rescued by Abi-1 S323A (but not Abi-1 S323D) re-expression. This regulation is generalizable beyond brain cancer, as GTP supplementation promoted DNA repair and p-Abi1 (S323) dephosphorylation in non-malignant cells and protected mice from RT-mediated gastrointestinal injury and bleomycin-induced pulmonary fibrosis. CONCLUSION: The GTP-Rac1-PP5-Abi-1 signaling axis links metabolism and DNA repair. Disrupting this pathway can overcome cancer resistance to genotoxic therapy while augmenting it can mitigate genotoxic injury of normal tissues. Citation Format: Weihua Zhou, Zitong Zhao, Angelica Lin, John Yang, Jie Xu, Kari Wilder-Romans, Annabel Yang, Andrew J. Scott, Jing Li, Sumeet Solanki, Jennifer Speth, Natalie Walker, Ayesha U. Kothari, Yangyang Yao, Erik R. Peterson, Navyateja Korimerla, Christian K. Werner, Jessica Liang, Janna Jacobson, Sravya Palavalasa, Alexandra M Obrien, Ameer L Elaimy, Sean P. Ferris, Shuang G. Zhao, Jann N. Sarkaria, Balázs Győrffy, Shuqun Zhang, Wajd N. Al-Holou, Yoshie Umemura, Meredith A Morgan, Theodore S. Lawrence, Costas A. Lyssiotis, Marc Peters-Golden, Yatrik M. Shah, Daniel R. Wahl. GTP signaling links metabolism, DNA repair, and responses to genotoxic stress [abstract]. In: Proceedings of the AACR Special Conference on Brain Cancer; 2023 Oct 19-22; Minneapolis, Minnesota. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_1):Abstract nr A004.