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733 Background: VHL disease is a rare hereditary condition that causes abnormal tumor growth in multiple organs, including renal cell carcinoma (RCC), central nervous system (CNS) hemangioblastomas (Hb), pancreatic neuroendocrine tumors (pNET), and other tumors. Repeated surgeries are often required due to ongoing tumor recurrences and can lead to complications such as chronic kidney disease, pancreatic insufficiency, and neurological deficit. Belzutifan is a hypoxia-inducible factor inhibitor approved in the US for the treatment of VHL-associated RCC, CNS Hb, or pNET not requiring immediate surgery. This study aimed to quantify the annual rate and costs of VHL-related surgeries and surgical complications before and after belzutifan initiation. Methods: Surgeries were observed during the periods before and after belzutifan initiation in the single-arm phase 2 LITESPARK-004 trial (NCT03401788) among adults with VHL-RCC. Rates of RCC surgeries were obtained by fitting exponential survival models to: time from treatment initiation to the next renal surgery; and time (looking backward) from treatment initiation to the most recent renal surgery before treatment. Rates of surgeries related to other VHL manifestations were calculated as number of surgeries divided by person-years at risk, using all available post-treatment follow up (151 person-years; median [range] per patient: 29.2 [4.2-37.5] months) and equivalent person-years in the pre-treatment period. Complication risks per surgery and unit costs of surgeries and complications were obtained from a retrospective study on VHL within the Optum Clinformatics Data Mart (2000-2020). Annual per-patient costs of surgeries and complications were estimated in 2020 US dollars over the pre- and post-treatment periods from a US third-party payer perspective. Results: Among trial participants (N=61), the rate of RCC surgeries (surgeries/person-year) decreased 87% (0.108 to 0.014) after belzutifan initiation. The rate of other surgeries decreased 98% (0.265 to 0.007), with CNS Hb surgeries decreasing from 0.185 to 0.007, pNET surgeries from 0.013 to 0, adrenal lesion surgeries from 0.007 to 0, and retinal Hb surgeries from 0.060 to 0. Belzutifan was accordingly estimated to reduce per-patient average annual costs of surgeries and complications from $57,259 to $2,536. Conclusions: Healthcare costs of surgeries and surgical complications are substantial among patients with VHL-RCC. In a trial-based cost-consequence analysis, belzutifan was estimated to decrease annual surgery and complication costs by 96%, based on observed reductions in VHL-related surgeries. [Table: see text]

Approximately, 4% of Stage IV colorectal cancers (CRC) are microsatellite instability-high (MSI-H)/deficient mismatch repair (dMMR) tumors. Patients with metastatic MSI-H/dMMR CRC receiving conventional therapies experience lower response rates and tend to have worse overall survival compared with patients with microsatellite stable (MSS)/proficient mismatch repair (pMMR) CRC. Pembrolizumab received FDA approval in 2020 for first-line treatment of Stage IV MSI-H/dMMR CRC based on significantly longer progression-free survival versus standard of care (SoC, 5-fluorouracil-based therapy with or without bevacizumab or cetuximab). This study evaluated the cost-effectiveness of pembrolizumab vs. SoC as per KEYNOTE-177 and other first-line treatments for MSI-H/dMMR CRC from a US healthcare system perspective. A three-health-state partitioned-survival model was built using progression-free and overall survival data from KEYNOTE-177 and a network meta-analysis. Utilities were derived from KEYNOTE-177 EQ-5D-3L data. Drug acquisition, administration, AE, surgery, monitoring, subsequent treatment, and terminal care costs were included. Sensitivity and scenario analyses were performed, including utilizing a state-transition model structure and adopting a societal perspective. Over a lifetime time horizon, pembrolizumab and SoC were associated with total QALYs of 4.85 and 3.23, and total costs of $381,735 and $370,465, respectively, resulting in an ICER of $6,984 per QALY. QALY gains were mainly driven by extended survival with pembrolizumab. Pembrolizumab incurred higher drug acquisition costs relative to SoC but was cost-saving in terms of drug administration, AE, monitoring, subsequent treatment, and terminal care. Pembrolizumab dominated FOLFOX + panitumumab, FOLFOXIRI, and FOLFOXIRI + bevacizumab, and presented ICERs of $35,220 and $276 against XELOX and XELOX + bevacizumab. Results were robust to sensitivity and scenario analyses. Pembrolizumab is highly cost-effective for the first-line treatment of unresectable or metastatic MSI-H/dMMR CRC in the US at a willingness-to-pay threshold of $100,000/QALY.Key messagesPembrolizumab is a highly cost-effective option for the first-line treatment of patients with unresectable or metastatic MSI-H/dMMR colorectal cancer in the United States at a willingness-to-pay threshold of $100,000. Compared with the current standard of care for these patients, pembrolizumab:Increases survival due to delaying and preventing progression;Increases QALYs due to longer survival, improvement in HRQoL in the progression-free health state, and fewer Grade 3+ adverse events;Reduces costs associated with administering treatment, managing adverse events, monitoring post-progression disease, providing subsequent treatment, and providing terminal care; andReduces indirect health care costs when taking a societal perspective due to productivity gains from delaying and preventing progression and death, less frequent treatment administration and less frequent Grade 3+ adverse events. Pembrolizumab is a highly cost-effective option for the first-line treatment of patients with unresectable or metastatic MSI-H/dMMR colorectal cancer in the United States at a willingness-to-pay threshold of $100,000. Compared with the current standard of care for these patients, pembrolizumab: Increases survival due to delaying and preventing progression; Increases QALYs due to longer survival, improvement in HRQoL in the progression-free health state, and fewer Grade 3+ adverse events; Reduces costs associated with administering treatment, managing adverse events, monitoring post-progression disease, providing subsequent treatment, and providing terminal care; and Reduces indirect health care costs when taking a societal perspective due to productivity gains from delaying and preventing progression and death, less frequent treatment administration and less frequent Grade 3+ adverse events.

Introduction Pembrolizumab has been approved in the United States (US) for the first-line treatment of patients with advanced or metastatic urothelial carcinoma, who are ineligible for cisplatin-containing chemotherapy and with tumors expressing programmed death-ligand 1 (PD-L1) (Combined Positive Score ≥ 10), or ineligible for any platinum-containing chemotherapy regardless of PD-L1 status. Long-term KEYNOTE-052 data continue to demonstrate pembrolizumab’s meaningful, durable, and well-tolerated antitumor activity. This study evaluates the cost-effectiveness of pembrolizumab versus carboplatin plus gemcitabine as first-line treatment for cisplatin-ineligible patients who have PD-L1–positive tumors from a US third-party healthcare payer’s perspective. Patients and Methods A partitioned survival model containing 3 health states (progression-free, progressed, and death) was developed. A simulated treatment comparison and a network meta-analysis were conducted to estimate the comparative efficacy of pembrolizumab versus carboplatin-based chemotherapy. Overall survival, progression-free survival, time on treatment, adverse events, and utilities were modeled using the final analyses of the KEYNOTE-052 trial and 4 studies for carboplatin plus gemcitabine. Cost data were estimated using US standard sources and real-world data. Deterministic, probabilistic, and scenario analyses were conducted to assess the robustness of the results. Results Over 20 years, pembrolizumab resulted in a mean gain of 2.58 life-years, 2.01 quality-adjusted life-years, and additional costs of $158,561, leading to an incremental cost-effectiveness ratio of $78,925/quality-adjusted life-year compared with carboplatin plus gemcitabine. Conclusion This study suggests that pembrolizumab is cost-effective compared with carboplatin plus gemcitabine as a first-line therapy for patients with advanced or metastatic urothelial carcinoma who are PD-L1–positive.

Aims: Pembrolizumab demonstrated significantly prolonged overall survival (OS) vs. chemotherapy in the Phase III KEYNOTE-045 trial, and is approved in the US for the treatment of patients with locally advanced or metastatic urothelial carcinoma (mUC) who progressed after platinum-based chemotherapy. Using longer follow-up and individual patient-data from KEYNOTE-045, this study evaluates the cost-effectiveness of pembrolizumab vs. chemotherapy or atezolizumab from a US payer perspective. Materials and methods: A partitioned-survival model was developed over a 20-year time horizon. Progression-free survival (PFS) and OS for pembrolizumab and chemotherapy were extrapolated using a piecewise modelling approach, where patient-level data from KEYNOTE-045 were used for the initial period followed by parametric distributions. OS of atezolizumab was estimated by indirect treatment comparisons based on KEYNOTE-045 and IMvigor211. Different scenarios were explored in the absence of indirect comparisons on PFS and time-on-treatment (ToT) between pembrolizumab and atezolizumab. Drug acquisition/administration, disease management, adverse events, and terminal care costs were considered. Results: Compared with chemotherapy, pembrolizumab resulted in a mean gain of 1.33 life-years and 1.14 quality-adjusted life-years (QALYs) and an incremental cost of $106,299, yielding an incremental cost-effectiveness ratio of $93,481/QALY gained. Pembrolizumab dominated atezolizumab in extending patients’ life by 0.89 years and 0.76 QALYs, while reducing costs by $26,458. Key drivers of cost-effectiveness included survival extrapolation, OS hazard ratio of pembrolizumab vs. atezolizumab, and time horizon. Pembrolizumab had a 66% and 100% probability of being cost-effective vs. chemotherapy and atezolizumab, respectively, at a $100,000 willingness-to-pay threshold. Limitations and conclusions: Uncertainties remain with extrapolated PFS and OS for pembrolizumab, OS indirect comparison, and ToT for atezolizumab. Despite these limitations, the model used robust methods to estimate key clinical endpoints with patient-level data from longer follow-up of KEYNOTE-045. Pembrolizumab dominates atezolizumab and is very likely cost-effective vs. chemotherapy in 2 L mUC at a $100,000 willingness-to-pay threshold.

Objectives: Real-time virtual sonography (RVS) is a promising navigation technique for percutaneous radiofrequency ablation (RFA) treatment, especially in ablating nodules poorly visualized on conventional ultrasonography (US). However, its cost-effectiveness has not been established. The purpose of this study is to evaluate the cost-effectiveness of RVS navigated RFA (RVS-RFA) relative to US guided RFA (US-RFA) in patients with small hepatocellular carcinoma (HCC) in China, from the modified societal perspective.Methods: A state-transition Markov model was created using TreeAge Pro™ 2012. The parameters used in the model, including natural history of HCC patients, procedure efficacy and related costs, were obtained from a systematic search of literature through PubMed, EMBASE, and Science Citation Index databases. The simulated cohort was patients with solitary, small HCC (Results: In this cohort of difficult cases, RVS-RFA was a preferred strategy saving 2,467 CNY ($392) throughout the patient's life while gaining additional 1.4 QALYs compared with conventional US guidance. The results were sensitive to the efficacy of US-RFA and RVS-RFA including complete ablation rate and local recurrence rate, the median survival for patients with progressive HCC, the probability of performing RFA for recurrent HCC, and the cost of RVS navigation, disposable needle or hospitalization.Conclusions: RVS-RFA is a dominant strategy for patients with small HCC unidentifiable in B-mode US, in terms of cost savings and QALYs gained, relative to the conventional US-guided method.

93 Background: Pembrolizumab is indicated as first-line therapy for cisplatin-ineligible patients with locally advanced or metastatic urothelial carcinoma (mUC) whose tumors express PD-L1 with a combined positive score (CPS) ≥ 10. This study aims to evaluate the cost‐effectiveness of pembrolizumab versus carboplatin plus gemcitabine in this setting from the US payer perspective. Methods: A partitioned-survival model was developed to measure the costs and effectiveness over a 20-year time horizon with an annual discount of 3%. Clinical outcomes of overall survival (OS) and progression-free survival, safety outcomes and time on treatment were modeled using data from the KEYNOTE-052 clinical trial for pembrolizumab and four clinical trials for carboplatin plus gemcitabine. Because clinical trials directly comparing these treatment strategies are not available, a simulation treatment comparison and a network meta-analysis were conducted to estimate comparative efficacy. Quality of life data extracted from EQ-5D questionnaires administered in KEYNOTE-052 were used to estimate utility, while cost data were estimated using US pricing lists and real-world data. Deterministic and probabilistic sensitivity analyses were conducted to assess the robustness of the results. Pembrolizumab was also compared with gemcitabine monotherapy in the scenario analyses. Results: Pembrolizumab was associated with a survival gain of 2.47 years and 1.90 quality adjusted life years (QALY), an incremental cost of $155,238, and an incremental cost per QALY gained of $81,493 versus carboplatin plus gemcitabine. Results were most sensitive to the time horizon, discount rate, pembrolizumab dosing intensity and OS hazard ratio. Pembrolizumab had 87% or 100% probability of being cost-effective vs. chemotherapy at a $100,000 or $150,000 willingness-to-pay threshold, respectively. Conclusions: Pembrolizumab appears cost-effective versus carboplatin plus gemcitabine as first-line treatment of cisplatin-ineligible and PD-L1 positive mUC patients in the US. The comparison of pembrolizumab with gemcitabine monotherapy yields similar conclusions.

e16010 Background: Pembrolizumab is approved by the US Food and Drug Administration for the treatment of locally advanced or metastatic urothelial carcinoma (mUC) following platinum-based chemotherapy, based on results from KEYNOTE-045. In this randomized phase 3 trial, pembrolizumab significantly prolonged overall survival (OS) vs. chemotherapy in mUC patients (cut-off: Oct 26, 2017). The current analysis evaluates the cost-effectiveness of pembrolizumab vs. standard-of-care chemotherapy (docetaxel or paclitaxel) as second-line (2L) treatment for mUC, from a US payer perspective. Methods: We developed a partitioned-survival model to measure the costs and effectiveness over a 20-year time horizon to capture long-term costs and benefits from the treatments. Clinical efficacy, time on treatment, safety and utility data were derived from KEYNOTE-045. OS and progression-free survival were extrapolated beyond the trial period using piecewise models, i.e., Kaplan-Meier data followed by parametric function. Costs (in 2018 $US) for drug acquisition/administration, disease monitoring, adverse events management and terminal care were included. Costs and outcomes were discounted at 3% per year. Deterministic and probabilistic sensitivity analyses were conducted to assess the robustness of the results. Results: Pembrolizumab resulted in a mean gain of 1.33 life years (LYs) and 1.14 quality-adjusted life-years (QALYs) at an incremental cost of $103,861 vs. chemotherapy. The incremental cost-effectiveness ratios were $91,103/QALY and $78,254/LY. Key drivers of cost-effectiveness were extrapolation methods for OS data, time horizon and utility values. Pembrolizumab had a 72% or 100% probability of being cost-effective vs. chemotherapy at a $100,000 or $150,000 willingness-to-pay threshold, respectively. Conclusions: Pembrolizumab appears to be cost-effective vs. docetaxel or paclitaxel monotherapy as 2L mUC therapy when accounting for durable survival seen in a subset of patients receiving pembrolizumab. The model was established based on robust estimates, with key clinical endpoints directly drawn or derived from patient level data in KEYNOTE-045.

Virus-induced gene silencing using artificial microRNAs (MIR VIGS) is a newly developed technique for plant reverse genetic studies. Traditional virus-induced gene silencing (VIGS) assays introduce a large gene fragment, which is expressed and then converted into small RNAs by the endogenous siRNA-based gene silencing machinery of the plant host. By contrast, MIR VIGS uses well-designed miRNAs to induce RNA-mediated silencing of the target gene. Using a single artificial miRNA can provide greater specificity by reducing off-target effects. Here, we describe a detailed protocol for MIR VIGS in Nicotiana benthamiana using a modified Cabbage leaf curl virus (CaLCuV)-based vector.

Virus-induced gene silencing using artificial microRNAs (MIR VIGS) is a newly developed technique for plant reverse genetic studies. Traditional virus-induced gene silencing (VIGS) assays introduce a large gene fragment, which is expressed and then converted into small RNAs by the endogenous siRNA-based gene silencing machinery of the plant host. By contrast, MIR VIGS uses well-designed miRNAs to induce RNA-mediated silencing of the target gene. Using a single artificial miRNA can provide greater specificity by reducing off-target effects. Here, we describe a detailed protocol for MIR VIGS in Nicotiana benthamiana using a modified Cabbage leaf curl virus (CaLCuV)-based vector.

*The hairpin-based RNA interference (RNAi) technique plays an important role in exploring gene function in plants. Although there are several methods for making hairpin RNA (hpRNA) constructs, these methods usually need multiple relatively laborious, time-consuming or high-cost cloning steps. Here we describe a one-step, zero-background ligation-independent cloning (OZ-LIC) method for making intron-containing hpRNA (ihpRNA) constructs by our vector pRNAi-LIC. *To generate the ihpRNA constructs with zero-background, this method only requires treating two PCR products of target gene flanked with different LIC sequences and SmaI-linearized pRNAi-LIC vector by T4 DNA polymerase respectively, and then transforming these treated DNA mixture into Escherichia coli. *The ihpRNA constructs generated with our OZ-LIC RNAi vector can efficiently induce not only transient silencing of the exogenous marker genes and the endogenous resistance-related Nicotiana benthamiana SGT1 gene, but also stable transgenic suppression of Arabidopsis SGT1b gene. *Our new OZ-LIC method and RNAi vector will represent a powerful tool for gene knockdown in plants and may facilitate high-throughput determination of plant gene function.