Orme, Jacob J.

Abstract Retinoblastoma (RB) protein can exert tumor suppressor functions even when it becomes phosphorylated. It is thus essential to understand how phosphorylated RB (p-RB) expression and function are regulated. Here, we demonstrated that RING finger domain protein TRIM28 bound and promoted ubiquitination and degradation of CDK4/6-phosphorylated RB protein. SETDB1, a known TRIM28 binding partner, protected p-RB from degradation through the binding of methylated RB by its Tudor domain independent of its methyltransferase activity. SETDB1 was found to be frequently overexpressed due to gene amplification and positively correlated with p-RB in prostate cancer patient specimens. Inhibition of SETDB1 expression using a gene-specific antisense oligonucleotide (ASO) reduced tumor growth but accelerated RB protein degradation, limiting the therapeutic efficacy. However, coadministration of the CDK4/6 inhibitor palbociclib blocked ASO-induced RB degradation and resulted in a much greater cancer-inhibitory effect than each inhibitor alone both in vitro and in vivo. This study identified CDK4/6-dependent, TRIM28-mediated proteasomal degradation as a mechanism of RB inactivation and reveals SETDB1 as a key inhibitor of this process. Our findings suggest that combined targeting of SETDB1 and CDK4/6 represents a viable approach for the treatment of cancers with SETDB1 gene amplification or overexpression. Significance: The identification of a role for TRIM28 and SETDB1 in regulating CDK4/6-phosphorylated RB stability uncovers a combination strategy using CDK4/6 and SETDB1 inhibition to decrease RB degradation and inhibit cancer growth.

PURPOSE: For the past 5 years, most major antiemesis guidelines have included olanzapine-containing regimens among the recommended options for prophylaxis with highly emetogenic chemotherapy (HEC). We analyzed the uptake of olanzapine in clinical practice and the changing composition of multidrug antiemetic regimens. METHODS: A retrospective analysis was performed using an OptumLabs deidentified database of medical and pharmacy claims, which was filtered for patients starting HEC in the interval of 2006 to Q2 of 2021. Descriptive statistics were used to analyze patient characteristics and year-by-year antiemetic prescribing patterns, coinciding with cycles 1 and 2 of chemotherapy. RESULTS: A total of 63,154 distinct patients were included. The median age was 58 years (range, 18-88). Breast (45.2%) and hematologic (20.8%) cancers were the most common diagnoses. In 2016, olanzapine was prescribed to 1.4% of patients with cycle 1 of HEC. Prescriptions increased modestly each year, and by 2021, 13.9% of patients received olanzapine with their first cycle of chemotherapy. An additional 5.7% of patients received olanzapine for breakthrough symptoms or enhanced prophylaxis during cycle 2. In 2021, more than three-quarters of patients were prescribed antiemetics in a guideline-concordant manner, with an olanzapine-containing quadruplet (12.2%), an NK1-receptor antagonist triplet (64.5%), or an olanzapine triplet (suppressed for small sample size). CONCLUSION: Despite inclusion in major antiemesis guidelines, there has been relatively slow uptake of olanzapine for prophylaxis with HEC. This finding highlights the challenges of disseminating information and keeping prescribing systems updated with the newest evidence in supportive oncology.

232 Background: Olanzapine has an important role in preventing and treating nausea and vomiting from highly emetogenic chemotherapy (HEC). This drug, for the last 5 years, has been a component of most major antiemesis guidelines. The aim of the current study was to assess how often olanzapine has been prescribed for patients receiving HEC. Methods: A retrospective analysis was performed using an OptumLabs de-identified clinical database of medical and pharmacy claims. The database was filtered for patients starting HEC in the interval of 2006 to Q2 of 2021. Descriptive statistics were used to analyze patient characteristics and year-by-year antiemetic prescribing patterns, coinciding with cycles 1 and 2 of chemotherapy. Results: A total of 63,154 distinct patients were included. The median age was 58 years (range, 18-88). Over a quarter of the patients identified as Black, Hispanic, Asian, or other. Breast (45.2%) and hematologic (20.8%) cancers were the most common diagnoses. In 2016, olanzapine was prescribed to only 1.4% of patients with cycle 1 of HEC. Prescriptions increased modestly each year, and by 2021, 13.9% of patients received olanzapine with their first cycle of chemotherapy. An additional 5.7% of patients received olanzapine for breakthrough symptoms or enhanced prophylaxis during cycle 2. In 2021, over three-quarters of patients were prescribed antiemetics in a guideline concordant manner, with either an olanzapine-containing quadruplet (12.2%), an NK1 receptor antagonist triplet (64.5%), or an olanzapine triplet (exact number suppressed due to small sample size). Conclusions: The rate of olanzapine prescribing is less than might be expected following its inclusion in major antiemesis guidelines. This finding highlights the challenges of disseminating information and keeping prescribing systems updated with the newest evidence in supportive oncology.

Abstract NRG-1 signals through epidermal growth factor receptor (EGFR) family members. Despite promising preclinical data, HER2 blockade in prostate cancer has failed to improve outcomes in clinical trials.1-4 We have discovered a novel complex systemic role of NRG-1 that drives sensitivity and resistance to androgen deprivation therapy (ADT) in castration-sensitive (CSPC) and castration resistant prostate cancer (CRPC), respectively. Significantly, sensitivity to ADT can be restored in CRPC by manipulating NRG-1 signaling. Our data posit NRG-1 as a systemic “switch” in prostate cancer. Plasma NRG-1 is elevated in our cohort of patients with metastatic CRPC (mean 4.9ng/ml) versus healthy controls (mean 3.2ng/ml, p<0.0001) or metastatic CSPC (mean 3.4ng/ml, p<0.0001). Paradoxically, high systemic NRG-1 predicted superior OS and PFS in CSPC but inferior clinical outcomes in CRPC. Consistently, opposite cell survival between LNCaP (CSPC) vs Du145 & PC3 (CRPC) was observed with recombinant human NRG-1 and enzalutamide (ENZ). ENZ combined with increasing NRG-1 concentration induced LNCaP cell death in an additive manner, but NRG-1 rescued Du145 & PC3 from ENZ-induced death in a dose-dependent manner. We next hypothesized that differential NRG-1 downstream signaling is mediated by engagement with distinct EGFR receptor dimers. While HER2 expression is similar, LNCaP express higher HER3 than Du145 & PC3. High ratio of HER2 to HER3 in Du145 & PC3 mirrors clinical reports of HER2 upregulation in CRPC5,6 and also predicts patient survival in the Stand Up to Cancer cohort.7 Significantly, we recapitulated the CRPC phenotype in LNCaP by inducing HER2 overexpression, HER3 suppression, and chemically-mediated HER2/HER3 dimerization. Conversely, HER2 knockdown sensitized Du145 cells to ENZ. Next, we queried composite single-cell whole human8 and CRPC9 transcriptomes for NRG-1 expression and discovered that the source of NRG-1 is the patients’ own mesenchymal stem cells (MSCs). Bone-derived MSC outgrowth cells produced copious NRG-1, which was increased substantially by coincubation with prostate cancer cell supernatants. Importantly, we were able to manipulate MSCs to reduce their NRG-1 production as a possible clinical translation. Similarly, patients treated with these compounds showed significant reduction in plasma NRG-1 levels after treatment. Additional clinical studies are pending. Together, our observations confirm that NRG-1 has differential signaling: HER3 homodimerization leads to prostate cancer cell death, whereas heterodimerization of HER3 with HER2 leads to prostate cancer cell survival via ADT resistance in a plasma NRG-1 dependent manner. Consequently, HER2 and HER3 receptor availability determine the molecular switch of NRG-1 in prostate cancer. Therefore, NRG-1 can be both a prognostic marker and therapeutic target in CRPC, and multiple clinical trials are pending. Citation Format: Jacob Orme, Roman Thaler, Dejie Wang, Siven Chinniah, Jacob Hirdler, Fernando Quevedo, Lance Pagliaro, Kwon Eugene, Alan Bryce, Brian Costello, Haojie Huang, Sean Park. Mesenchymal stem cell-derived systemic NRG-1 mediates a targetable molecular switch in metastatic prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 397.

6552 Background: Significant amounts of expensive oncology drugs are discarded resulting in waste and financial consequences for patients. Beginning in 2023, the Infrastructure Investment and Jobs Act (IIJA) will require drug manufacturers to refund Medicare for any single-use drugs where greater than 10% of the drug is wasted. We explored potential IIJA-associated savings through assessment of patterns in spending for discarded oncology agents between 2017-2020. Methods: We utilized the Medicare Part B Discarded Drug Units database from 2017-2020. Using J codes, we extracted spending and reimbursement data for discarded medications for antineoplastic and classical hematology therapies. The primary outcome was identification of therapies with high percentage of waste and the economic impact of retroactive application of the IIJA for discarded therapies. Results: Medicare Part B utilization data was extracted for a median 77 (64-152) oncologic therapies per year with median reimbursement for discarded treatments of $590 M ($566-616). From 2017-2020, bortezomib, romiplostim, and nab-paclitaxel were consistently among the top 5 therapies by value of wasted product. Pembrolizumab waste by value declined significantly after 2017 following transition to fixed dosing. In 2020, the top 5 therapies by value of wasted product were bortezomib, nab-paclitaxel, trastuzumab, romiplostim, and cabazitaxel with a value of $278 M. In 2020, the agents with the highest percentage of wasted product were bortezomib (27%), cabazitaxel (28%), decitabine (23%), topotecan (23%), and azacitidine (22%) with a collective discarded value of $160 M. Notably, these agents have weight-based dosing and single-use vials. Based upon the average number of drug claims per recipient and volume of product discarded, eliminating drug waste would allow an additional 6564 patients to receive treatment with discarded bortezomib. The number of additionally treated patients for the other top 5 agents: cabazitaxel (1216), decitabine (1509), topotecan (291), and azacitidine (2682). Retroactive application of IIJA policy would have impacted a median 20 (12-26) oncology agents resulting in median annual cost savings of $153 M (142-157) and the median annual spending on wasted oncology therapies would decline to $440 M (410-466). Conclusions: The IIJA would have yielded a median annual savings of $153 M in Medicare spending if applied retroactively. Given a 10% waste cutoff, a limited number of agents would be targeted by this legislation. In our study, we observe that drugs associated with weight-based dosing and single-use drug vials account for most drug waste. Strategies to minimize discarded units (through storage of unused product, approval of multi-dose vial formulations, or fixed-dose therapies) could yield substantial savings while enabling health equity in collaboration with communities with difficult access to these drugs.

PURPOSE: Precision oncology promises improved outcomes but the cost-effectiveness and accessibility of targeted therapies is debatable. We report price change patterns from 2015 to 2019 for several oral anticancer medications for common solid tumor malignancies. METHODS: We collected provider utilization and payment data from the public Medicare Part D database and extracted drug price information for commonly prescribed targeted oral anticancer agents for lung, breast, and prostate cancer. We then calculated median Pearson correlation coefficient values for various drugs (containing more than two data points) within each therapeutic class. We also calculated compound annual growth rates (CAGRs) for medication costs within each class and compared them with the consumer price index (CPI). RESULTS: Our study included six epidermal growth factor receptor inhibitors (EGFRi; one generic), five anaplastic lymphoma kinase inhibitors (ALKi), two B-Raf inhibitors (BRAFi), three hormonal agents (one generic), three cyclin-dependent kinases 4 and 6 inhibitors (CDK4/6i), two poly-ADP-ribose inhibitors (PARPi), and seven antiandrogen agents (two generic). The median (range) Pearson correlation coefficient values for cost of drugs within each therapeutic class were 0.967 (0.915-0.978) for EGFRi, 0.981 (0.966-0.989) for ALKi, 0.996 for BRAFi, 0.994 (0.992-0.999) for CDK4/6i, 0.855 for PARPi, and 0.442 (–0.522 to 0.962) for antiandrogens. Therapies with two or fewer data points (generic erlotinib, dacomitinib, abiraterone, apalutamide, and darolutamide) were excluded. The median CAGRs in costs over the 5-year period were 4.56% (EGFRi), 6.40% (ALKi), 2.58% (BRAFi), 5.48% (hormonal agents), 5.21% (CDK4/6i), 27.29% (PARPi), and 34.8% (antiandrogens). The CPI over 5 years was 2.26%/year, and the average inflation rate was 1.90%/year. CONCLUSION: The median CAGR in costs for modern oral precision-driven cancer therapeutic classes mostly outpaced CPI and the average inflation. Increase in cost within the same class should be weighed against incremental clinical benefit for the patients to ensure that rising costs do not limit access to targeted therapies.

Background Patients with metastatic melanoma rely on PD-(L)1 immunotherapy, but only one-third of patients experience treatment response and all initial responders eventually develop resistance. Tumour-derived extracellular vesicles expressing Programmed death ligand 1 (evPD-L1) and soluble Programmed death ligand 1 (sPD-L1) in peripheral blood of patients with melanoma limit PD-(L)1 immunotherapy and correlate with poor survival. Therapeutic plasma exchange (TPE) removes immunosuppressive evPD-L1 and sPD-L1. We hypothesise that TPE may rescue and restore antimelanoma immunity. Methods In this two-arm study, 60 patients with metastatic melanoma progressing on checkpoint inhibition will be accrued. All patients will undergo radiotherapy on days 1–5 (at least one measurable lesion will not be irradiated) and ongoing checkpoint inhibition on day 8 and every 2–3 weeks per standard of care. Patients with baseline sPD-L1 level of ≥1.7 ng/mL and adequate clinical capacity will be enrolled in the TPE intervention arm and will undergo TPE on days 5–7, in addition to standard of care radiotherapy and immunotherapy. Other patients will remain in the standard of care arm. The primary endpoint of the study is to evaluate safety. Secondary endpoints include kinetics of sPD-L1 and evPD-L1 and clinical response by RECIST (Response Evaluation Criteria in Solid Tumors) criteria. Study registered at ClinicalTrials.gov ( NCT04581382 ). Ethics and dissemination This trial has been approved by the Mayo Clinic Institutional Review Board. It will assess the safety and feasibility of TPE in improving outcomes for PD-(L)1 inhibitor immunotherapy in melanoma. Data will be maintained on a secure database with deidentified patient information. Data will be shared on publication in a peer-reviewed journal without the aid of professional writers. If successful, this trial will lay the ground for phase II studies that will include cancer treated with PD-(L)1 inhibitors which may benefit from TPE such as renal, bladder and lung cancers. Trial registration number NCT04581382 .

Platinum-based chemotherapy is the standard of care with concern to first-line systemic therapy for metastatic disease in urothelial cancer (UC). Resistance to chemotherapy despite an initial response is linked with the ability to remove platinum-based DNA adducts and to repair chemotherapy-induced DNA lesions by various DNA repair proteins. The Rad9-Rad1-HUS1 complex that is loaded onto DNA at sites of damage is involved in checkpoint activation as well as DNA repair. Here, we addressed for the first time the potential influence of HUS1 expression in urothelial carcinogenesis (using two human basal urothelial cancer cell lines UM-UC-3 and HT1197) and its role as a potential therapeutic target for predicting responses to platinum-based chemotherapy. Specific inhibition of HUS1 expression in both cell lines was achieved by specific siRNA and validated by Western blot. In order to define the possible importance of HUS1 in the regulation of cellular proliferation, parental and resistant cells were treated with increasing concentrations of either control or HUS1 siRNA. HUS1 protein expression was observed in both human basal urothelial cancer cell lines UM-UC-3 and HT1197. In cisplatin-sensitive cells, knock-down of HUS1 inhibited cellular proliferation in the presence of cisplatin. On the contrary, knock-down of HUS1 in resistant cells did not result in a re-sensitization to cisplatin. Finally, RNAseq data from the Cancer Genome Atlas provided evidence that HUS1 expression is a significant prognostic factor for poor survival in UC patients. In summary, HUS1 may acts as an oncogene in UC and might be a key determinant of the cellular response to cisplatin-based chemotherapy.

Abstract The second-generation antiandrogens have achieved an ever-growing list of approvals and indications in subsets of prostate cancer. Here, we provide an overview of second-generation antiandrogen trials and FDA approvals and outline a rational sequencing approach for the use of these agents as they relate to chemotherapy and other available treatment modalities in advanced prostate cancer. All published phase II-III randomized controlled trials reporting outcomes with the use of second-generation antiandrogens in prostate cancer are included as well as all published trials and retrospective studies of second-generation antiandrogen sequencing and/or combinations. Complete tabular and graphical representation of all available evidence is provided regarding the use and sequencing of second-generation antiandrogens in prostate cancer. In metastatic castration-resistant prostate cancer, evidence suggests prioritization of abiraterone before chemotherapy, chemotherapy after second-generation antiandrogen failure, and postchemotherapy enzalutamide in select patients to maximize agent efficacy and tolerability. We conclude that a rational, optimized sequencing of second-generation antiandrogens with other treatment options is feasible with present data.