Anderson, Ethan J.

727 Background: Despite the availability of targeted therapies like erdafitinib for pts with aUC with susceptible genomic alterations, the rate of NGS testing remains low at 32% in the United States (Hage Chehade...Swami, JAMA Network Open, 2024). Furthermore, limited data exist regarding the timing of NGS testing in relation to the time of death. Herein, we sought to assess the rates of NGS testing at the end of life in pts with aUC in a real-world patient population. Methods: A de-identified nationwide Flatiron Health electronic health record (EHR)-derived database was used to extract patient-level data. Inclusion criteria: pts who received NGS testing (blood/tissue) and who had a date of death recorded. The analytic cohort included pts diagnosed with aUC between 1/1/2011 and 11/14/2022 who received first NGS testing results between 5/3/2012 and 12/21/2022. The time difference between each pt’s first NGS result delivered and death was calculated, and thereafter, pts were categorized into 3 categories: pts receiving results > 3 months (mo) before death, within 3 mo of death, or after death. The frequency and percentages of the 3 categories were reported, as well as by year of death. The percentages in each category were compared between 2019 (year of erdafitinib approval) and 2022 (last year in dataset) to evaluate changes in NGS testing trend. Results: Among 12,157 pts with aUC in the dataset, 1,637 had both a recorded date of death and underwent NGS testing, and were eligible and included in final analysis. The median age was 72 (IQR 66 – 79). The majority were male (73%), White non-Hispanic (76%), and treated in community practice (86%). 68.2% received NGS results > 3 mo before death (n = 1,117), 28.3% received results within 3 mo of death (n = 464), and 3.4% of NGS results were reported after death (n = 56). In pts who died in 2019 versus 2022, the percentage of pts receiving NGS results > 3 mo before death increased from 61% to 75%, while the percentage of pts receiving results within 3 months decreased from 33% to 22%, and the percentage of NGS results reported after death declined from 5.2 to 2.7%. Baseline characteristics (including race-ethnicity, insurance plan, practice type [academic vs. community]) in these categories will be presented at the meeting. Conclusions: Our findings suggest that a sizeable number of pts with aUC (∼ 32%) received their first NGS testing results towards the end of life, highlighting the need to integrate genomic testing earlier during the course of the disease to optimize benefit with targeted therapies. These results could inform clinical practice and therapeutic decisions in the clinic. CHC, YJ: Equal contribution; US, NA: Senior authors.

75 Background: The Rx landscape of pts with mCRPC has recently evolved with the approval of lutetium-177-PSMA-617 (Lu-177) and poly(ADP) ribose polymerase inhibitors (PARPi) either as single agents or as combinations with an androgen receptor pathway inhibitor (ARPI) [PMID: 37442702]. However, real-world data on the uptake of these agents are lacking. Herein, we sought to assess the Rx patterns and attrition rates of pts with mCRPC in the era of newly approved therapies. Methods: The de-identified nationwide Flatiron Health Electronic-Health Record (EHR)-derived database was used to extract pt-level data. Eligibility criteria: diagnosis of mCRPC and Rx line (L) information. The data cut-off date was 5/31/2024. Rx patterns in each line of therapies were summarized using frequency and percentages. All analysis was done using R version 4.2.3. Results: Of the overall cohort of 24,105 pts with metastatic prostate cancer, 12,333 pts diagnosed with mCRPC between 1/1/2013 and 5/9/2024 met the eligibility criteria and were included. Rx trends are summarized (Table). Of pts receiving 1L Rx, 61% of pts received 2L therapy, and 35% received 3L therapy. Androgen receptor pathway inhibitor (ARPI) was the most common Rx in the 1L setting (73.7%), followed by taxane (10%) and sipuleucel-T (3.8%). In 2L, ARPI was again the most frequent Rx (46.8%), followed by taxane (23.6%). In 3L, taxane became the most frequent Rx (35.4%), followed by ARPI (26.2%) and radium-223 (4.9%). Rx trends per year will be presented in the meeting. Conclusions: In the current era,a high proportion of pts with mCRPC receiving 1L Rx do not receive a subsequent line of Rx (39% of pts do not receive 2L, and 65% do not receive 3L Rx). ARPIs and taxanes remain the most frequently used Rx options in most L of therapy. These findings highlight the need for better tolerated Rx, therapies with a novel mechanism of action, and improved access to care for our pts. Rx trends per year will be presented in the meeting. Rx patterns in pts with mCRPC. Rx 1L, n (%)N = 12,333 2L, n (%)N = 7475 3L, n (%)N = 4316 4L, n (%)N = 2339 5L, n (%)N = 1225 ARPI 9085 (73.7) 3503 (46.8) 1130 (26.2) 356 (15.2) 157 (12.8) PARPi-based therapies 93 (0.8) 185 (2.5) 142 (3.3) 98 (4.2) 47 (3.9) Platinum-based therapy 127 (1) 216 (2.9) 198 (4.6) 148 (6.3) 130 (10.6) Lu-177-based therapies 50 (0.4) 109 (1.5) 169 (3.9) 143 (6.3) 103 (8.4) Radium-223 183 (1.5) 241 (3.2) 213 (4.9) 125 (5.3) 79 (6.4) Sipuleucel-T 474 (3.8) 94 (1.3) 53 (1.2) 18 (0.8) 8 (0.7) Taxane 1240 (10) 1763 (23.6) 1526 (35.4) 935 (40) 393 (32) Pembrolizumab 24 (0.2) 41 (0.5) 36 (0.8) 27 (1.2) 29 (2.4) Other*/not-applicable** 665 (5.4)/392 (3.2) 1000 (13.4)/323 (4.3) 602 (14)/247 (5.7) 320 (13.7)/169 (7.2) 162 (13.3)/117 (9.5) *Includes drugs approved for mCRPC in combination with unapproved agents or clinical trial drugs. **Includes agents not approved for prostate cancer.

104 Background: Androgen deprivation therapy (ADT) intensification [ADT + androgen receptor-pathway inhibitor (ARPIs) +/- docetaxel] has been shown to improve survival outcomes in pts with mHSPC and is recommended as standard of care by all major guidelines. However, prior studies have shown underutilization of ADT intensification [PMID: 39191549]. There are limited updated and large-scale studies on the use of ADT intensification, beyond January 2023. In this study, we aimed to assess the treatment patterns of ADT intensification in real-world pts with mHSPC in the US, including data on those treated since January 2023. Methods: This retrospective study utilized the nationwide Flatiron Health Electronic Health Record (EHR) derived de-identified database. Eligibility: Pts diagnosed with mHSPC and availability of treatment information (ADT and/or line of therapy in mHSPC). The data cut-off date was 5/31/2024. Treatment patterns were summarized using frequency and percentages. All analysis was done using R version 4.2.3. Results: Among 24,105 pts with metastatic prostate cancer in the database, a total of 14,084 were eligible and included. The median age at metastatic diagnosis was 72 years (IQR 65 – 79), and 60% were White non-Hispanic. In the overall cohort (1/1/2013–5/15/2024), 56.8% received ADT monotherapy, and 37.7% received ADT intensification. Table summarizes the treatment patterns by year, highlightinga consistent increase in adoption of intensified ADT regimens, and a decline in use of ADT monotherapy. Notably, since January 2023, 76.8% pts with mHSPC received ADT intensification while only 17.3% of pts received ADT monotherapy. Conclusions: To our knowledge, this is the first and largest study to evaluate the current use of ADT intensification. These data indicate a notable improvement in the adoption of level 1 evidence (ADT intensification) in the treatment of pts with mHSPC. These encouraging data emphasize the benefits of continued efforts to promote guideline-concordant care and provide the current treatment landscape to design clinical trials. Treatment patterns by year in pts with mHSPC. Treatment 2013–2017n = 5,263(%) 2018n = 1,313 (%) 2019n = 1,407(%) 2020n = 1,353(%) 2021n = 1,483(%) 2022n = 1,556(%) 2023n = 1,459(%) 2024n = 250(%) ADT monotherapy 4,095 (77.8) 856 (65.2) 819 (58.2) 664 (49) 698 (47.1) 569 (36.6) 291 (20) 5 (2) ADT + ARPI 155 (2.9) 238 (18) 354 (25.1) 452 (33) 555 (37.4) 695 (44.7) 842 (58) 154 (61.6) ADT + Docetaxel 709 (13.5) 156 (12) 175 (12.4) 156 (12) 134 (9.0) 117 (7.5) 78 (5.3) 19 (7.6) Triplet(ADT + ARPI + Docetaxel) 6 (0.1) 2 (0.2) 1 (0.1) 2 (0.1) 9 (0.6) 82 (5.2) 166 (11.1) 53 (21.2) Other therapies 298 (5.7) 61 (4.6) 58 (4.1) 79 (5.8) 87 (5.9) 93 (6) 82 (5.6) 19 (7.6)

Monoamine Oxidase (MAO), an outer mitochondrial enzyme, catalyzes the oxidative deamination of neurotransmitters and biological amines, and in the process, produces a reactive aldehyde and H2O2. Our lab has recently shown that MAO activity (i.e., H2O2 production) in human right atrial myocardium is associated with postoperative atrial fibrillation. Furthermore, our lab has shown that diabetic patients have higher MAO‐A and ‐B content and rates of activity in this tissue, compared to nondiabetics. While recent studies have explored the connection between MAO and cardiac dysfunction, the chamber‐specific content and activity of MAO within the heart is still unknown. Therefore, we characterized the regional enzymatic activity of MAO‐A and ‐B based upon the hypothesis that the atria would have the highest MAO activity due to the greater density of local sympathetic nerve innervation in this region. For this study, porcine hearts were isolated from domestic pigs, as this model closely recapitulates the physiology of the human heart. One group of pigs were fed a high fat, high sucrose diet for 16 weeks to induce obesity/metabolic syndrome (n=4). Three MAO substrates (dopamine, norepinephrine, serotonin) and two isoform‐selective inhibitors (clorgyline=MAO‐A, deprenyl=MAO‐B) were used to characterize MAO activities. Enzyme content was measured using ELISA and confirmed with immunoblots. Kinetic analysis showed that, across all substrates, when normalized to tissue protein, the left atrium has the highest maximal MAO‐A and –B activity while the other three chambers are similar. Furthermore, maximal MAO activity in the left ventricle of pigs with metabolic syndrome is significantly greater (P<0.05) than left ventricle of control group. Our findings suggest that MAO activity differs by location in the heart (i.e., chamber heterogeneity). This information will be useful to inform future experimental and clinical pharmacology applications where MAO inhibitors might be used. Moreover, increased MAO in left ventricle of pigs with obesity/metabolic syndrome is important as it provides a rationale for exploring MAO inhibitors as therapeutic strategy to mitigate cardiac complications of diabetes. Support or Funding Information R01HL122863