Clinician Perspective on Once-Daily Zanubrutinib Dosing for B-Cell Malignancies at a Single Center.

Zanubrutinib, a next-generation, irreversible, highly potent, and selective Bruton tyrosine kinase inhibitor, is approved by the U.S. Food and Drug Administration to treat patients with B-cell malignancies in 2 dose regimens: 160 mg twice daily (BID) and 320 mg once daily (QD). Although the 160 mg BID regimen was the recommended phase 2 dose and more widely used in clinical trials, both regimens have yielded similar efficacy and safety. Currently, there is a lack of reported clinician experience on zanubrutinib QD versus BID practice patterns. This article provides perspectives on zanubrutinib dosing through interviews with 2 clinical care professionals at the Maryland Oncology Hematology Center, based on their experiences treating patients with Waldenström macroglobulinemia (WM) or chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL). Zanubrutinib QD is the preferred regimen for some physicians and pharmacists, as it may improve treatment adherence within weeks after initiation compared with BID dosing. According to the clinician interviews provided in this report, patients have reported positive experiences with QD dosing, including a reduced administration burden in those with complicated polypharmacy. Thus, observations from this single center indicate that the zanubrutinib QD regimen may offer benefits to both patients with WM or CLL/SLL and their clinical care teams and should be considered in patients receiving zanubrutinib.

Optimizing the dosing regimen of roxadustat in kidney transplant recipients with early post-transplant anemia.

INTRODUCTION: Roxadustat, an oral inhibitor of hypoxia-inducible factor prolyl hydroxylase domain enzymes, has been approved for the treatment of renal anemia. However, there is a lack of study on its pharmacokinetics in kidney transplant recipients (KTRs) with early posttransplant anemia (PTA). Therefore, the aim of this study is to elucidate the pharmacokinetic characteristics of roxadustat in KTRs with early PTA and optimize the dosing regimen. METHODS: A population pharmacokinetic (PopPK) analysis was performed based on 72-hour full concentration-time profiles collected from 52 Chinese KTRs. Covariates influencing exposure were assessed using stepwise covariate modelling. Monte Carlo simulations were conducted to recommend the dosing regimen for patients with different levels of covariates. RESULTS: PopPK analysis showed that the concentration-time data can be fully described by a two-compartment model. Body weight (BW) and direct bilirubin (DBIL) levels significant affected the apparent clearance of roxadustat. Based on the established model and the estimated exposures of roxadustat by Monte Carlo simulations, a recommended dosing regimen for KTRs with early PTA at varying BW and DBIL levels were developed. Roxadustat at 100 mg three times weekly were suitable for the majority of KTRs with a DBIL level around 3 µmol/L and BW between 50 and 75 kg. The required dose may need to be increased with higher BW and lower DBIL levels, while decreased with lower BW and higher DBIL levels. CONCLUSIONS: It was the first PopPK analysis of roxadustat in KTRs with early PTA, which provide a research basis for optimizing the dosing regimen.

Initial dosage optimization of olanzapine in patients with bipolar disorder based on model-informed precision dosing: a study from the real world.

Objectives: Olanzapine is used for treating bipolar disorder (BPD); however, the optimal initial dosing regimen is unclear. The present study aimed to investigate the optimal olanzapine initial dosage in patients with BPD via model-informed precision dosing (MIPD) based on a real-world study. Methods: Thirty-nine patients with BPD from the real-world study were collected to construct the MIPD model. Results: Weight, combined used quetiapine influenced olanzapine clearances in patients with BPD, where the clearance rates were 0.152:1 in patients with or without quetiapine under the same weight. We simulated olanzapine doses once a day or twice a day, of which twice a day was optimal. Without quetiapine, for twice-a-day olanzapine doses, 0.80, 0.70, and 0.60 mg/kg/day were suitable for 40- to 56-kg BPD patients, 56- to 74-kg BPD patients, and 74- to 100-kg BPD patients, respectively. With quetiapine, for twice-a-day olanzapine doses, 0.05 mg/kg/day was suitable for 40- to 100-kg BPD patients. Conclusion: This study was the first to investigate the optimal olanzapine initial dosage in patients with BPD via MIPD based on a real-world study, providing clinical reference for the precision medication of olanzapine in BPD patients.

Quantifying trade-offs between therapeutic efficacy and resistance dissemination for enrofloxacin dose regimens in cattle.

The use of antimicrobial drugs in food-producing animals contributes to the selection pressure on pathogenic and commensal bacteria to become resistant. This study aims to evaluate the existence of trade-offs between treatment effectiveness, cost, and the dynamics of resistance in gut commensal bacteria. We developed a within-host ordinary differential equation model to track the dynamics of antimicrobial drug concentrations and bacterial populations in the site of infection (lung) and the gut. The model was parameterized to represent enrofloxacin treatment for bovine respiratory disease (BRD) caused by Pastereulla multocida in cattle. Three approved enrofloxacin dosing regimens were compared for their effects on resistance on P. multocida and commensal E. coli: 12.5 mg/kg and 7.5 mg/kg as a single dose, and 5 mg/kg as three doses. Additionally, we explored non-FDA-approved regimes. Our results indicated that both 12.5 mg/kg and 7.5 mg/kg as a single dose scenario increased the most the treatment costs and prevalence of P. multocida resistance in the lungs, while 5 mg/kg as three doses increased resistance in commensal E. coli bacteria in the gut the most out of the approved scenarios. A proposed non-FDA-approved scenario (7.5 mg/kg, two doses 24 h apart) showed low economic costs, minimal P. multocida, and moderate effects on resistant E. coli. Overall, the scenarios that decrease P. multocida, including resistant P. multocida did not coincide with those that decrease resistant E. coli the most, suggesting a trade-off between both outcomes. The sensitivity analysis suggests that bacterial populations were the most sensitive to drug conversion factors into plasma ( ß ), elimination of the drug from the colon ( ϑ ), fifty percent sensitive bacteria (P. multocida) killing effect ( L s50 ), fifty percent of bacteria (E. coli) above ECOFF killing effect ( C r50 ), and net drug transfer rate in the lung ( γ ) parameters.

Reappraisal of the mechanism of cardiovascular responses to sympathomimetic amines in anaesthetised rats: dual α1-adrenoceptor and trace amine receptor mechanisms.

Established dogma is that sympathomimetic amines, including ß-phenylethylamine (PEA), increase blood pressure by releasing noradrenaline from sympathetic neurons. Recent evidence allowing longer contact with isolated immersed tissues indicates other mechanisms. The present study re-evaluates the mechanism of pressor responses to PEA in anaesthetised rats with longer exposure to infusions. Blood pressure and heart rate were monitored by cannulating a common carotid artery of anaesthetised male Sprague-Dawley rats. Drugs were administered by bolus doses or by 20-min infusions via a cannulated jugular vein. Increases in blood pressure by bolus doses of the α-adrenoceptor agonist, phenylephrine, were converted to depressor responses by prazosin and therefore α-adrenoceptor-mediated. Pressor responses to bolus doses of PEA were reduced. PEA infusions yielded four-phase responses: An initial increase in pressure (phase 1) blocked by prazosin was due to α-adrenoceptor vasoconstriction and a secondary fall in pressure (phase 2) due to vasodilatation by nitric oxide release. A later pressure increase (phase 3), further elevated after infusion stopped (phase 4), was not attenuated by prazosin and therefore non-adrenergic. This study showed for the first time that the sympathomimetic amine, ß-phenylethylamine, increases blood pressure by two mechanisms. The established indirect sympathomimetic mechanism applies to bolus dose administration. However, with prolonged exposure to infusions, an additional slow-onset sustained non-adrenergic blood pressure increase occurs, most likely mediated via trace amine-associated receptors (TAAR-1). This response will dominate with prolonged exposures in clinical practice. These results prompt a re-evaluation of established dogma on the indirect sympathomimetic mechanisms of these amines.

The Acute Kidney Intervention and Pharmacotherapy (AKIP) List: Standardized List of Medications That Are Renally Eliminated and Nephrotoxic in the Acutely Ill.

The objective of this project was to develop a standardized list of renally eliminated and potentially nephrotoxic drugs that will help inform initiatives to improve medication safety. Several available lists of medications from the published literature including original research articles and reviews, and from regulatory agencies, tertiary references, and clinical decision support systems were compiled, consolidated, and compared. Only systemically administered medications were included. Medication combinations were included if at least 1 active ingredient was considered renally dosed or potentially nephrotoxic. The medication list was reviewed for completeness and clinical appropriateness by a multidisciplinary team of individuals with expertise in critical care, nephrology, and pharmacy. An initial list of renally dosed and nephrotoxic drugs was created. After reconciliation and consensus from clinical experts, a standardized list of 681 drugs is proposed. The proposed evidence-based standardized list of renally dosed and potentially nephrotoxic drugs will be useful to harmonize epidemiologic and medication quality improvement studies. In addition, the list can be used for clinical purposes with surveillance in nephrotoxin stewardship programs. We suggest an iterative re-evaluation of the list with emerging literature and new medications on an approximately annual basis.

The many dimensions of combination therapy: How to combine antibiotics to limit resistance evolution.

In combination therapy, bacteria are challenged with two or more antibiotics simultaneously. Ideally, separate mutations are required to adapt to each of them, which is a priori expected to hinder the evolution of full resistance. Yet, the success of this strategy ultimately depends on how well the combination controls the growth of bacteria with and without resistance mutations. To design a combination treatment, we need to choose drugs and their doses and decide how many drugs get mixed. Which combinations are good? To answer this question, we set up a stochastic pharmacodynamic model and determine the probability to successfully eradicate a bacterial population. We consider bacteriostatic and two types of bactericidal drugs-those that kill independent of replication and those that kill during replication. To establish results for a null model, we consider non-interacting drugs and implement the two most common models for drug independence-Loewe additivity and Bliss independence. Our results show that combination therapy is almost always better in limiting the evolution of resistance than administering just one drug, even though we keep the total drug dose constant for a 'fair' comparison. Yet, exceptions exist for drugs with steep dose-response curves. Combining a bacteriostatic and a bactericidal drug which can kill non-replicating cells is particularly beneficial. Our results suggest that a 50:50 drug ratio-even if not always optimal-is usually a good and safe choice. Applying three or four drugs is beneficial for treatment of strains with large mutation rates but adding more drugs otherwise only provides a marginal benefit or even a disadvantage. By systematically addressing key elements of treatment design, our study provides a basis for future models which take further factors into account. It also highlights conceptual challenges with translating the traditional concepts of drug independence to the single-cell level.

Impact of clozapine once-daily versus multiple-daily dosing regimen on relapse in patients with treatment-resistant schizophrenia: A 1-year retrospective cohort study.

RATIONALE: Clozapine, the standard treatment for treatment-resistant schizophrenia (TRS), is generally recommended in a multiple-daily dosing regimen. However, it is commonly administered once daily in clinical practice. Few studies have compared the longitudinal clinical outcomes of these two dosing regimens. OBJECTIVE: To investigate the effect of once-daily versus multiple-daily dosing regimens of clozapine on relapse in patients with TRS. METHODS: This retrospective cohort study included patients with TRS who commenced treatment with clozapine during hospitalization and were discharged between April 2012 and January 2022 from a tertiary psychiatric hospital in Japan. Relapse, defined as a psychiatric exacerbation requiring re-hospitalization within the first-year post-discharge, was analyzed. Multivariable Cox proportional hazards regression analysis compared the relapse risk between once-daily and multiple-daily dosing regimens. A subgroup analysis was conducted to examine the potential interactions between dosing regimen and dose category (low versus high dose). RESULTS: Among 179 patients, 107 (59.8%) received clozapine once daily. No significant difference in the relapse risk was observed between once-daily and multiple-daily dosing regimens (adjusted hazard ratio [aHR]: 1.16; 95% confidence interval [CI]: 0.68-1.99; p = 0.58). However, in patients receiving high doses of clozapine (> 300 mg/day), multiple-daily dosing increased the relapse risk compared to once-daily dosing (aHR: 2.23; 95% CI: 1.00-4.97; p = 0.049). CONCLUSIONS: Once-daily clozapine dosing may not be associated with an increased relapse risk. The increased relapse risk in high-dose multiple-daily dosing may be confounded by unmeasured non-adherence. Further randomized controlled trials are required to validate these findings.

Ivermectin therapy for young children with scabies infection: a multicentre phase 2 non-randomized trial.

Background: Ivermectin, an effective treatment for scabies, is not licensed for children weighing <15 kg. Pharmacokinetic modelling has shown a 3 mg dose in young children (2-4 years, weighing 10-14 kg) achieves comparable drug exposure to a 200 µg/kg dose in children aged ≥5 years. This trial evaluated a 3 mg dose in young children. Methods: Multicentre, phase 2 trial in five health centres in Lao PDR. Children aged 2-4 years, weighing 10-14 kg with scabies received 3 mg ivermectin and had two plasma concentrations determined (Clinicaltrials.gov ID NCT05500326). On day 14, clinical outcomes and adverse effects were assessed, and a second dose given to complete treatment. The primary outcome was the mean plasma ivermectin exposure (AUC0-∞) after the first dose (compared to a historical control of Indigenous Australian children aged ≥5 years weighing ≥15 kg receiving 200 µg/kg). Secondary outcomes were clinical improvement and adverse effects. Findings: Overall, 100 children with a median age of 3.0 years (IQR 2.6-3.9) and weight of 11.9 kg (IQR 11.0-13.1) were enrolled. The mean observed ivermectin AUC0-∞ was comparable to the historical control group aged 5-11 years (815 µg h/L vs 953 µg h/L, p = 0.256). Complete resolution of scabies occurred in 90/99 children by day 14. Adverse effects were mild, occurring in 7/99. Interpretation: A 3 mg ivermectin dose in children aged 2-4 years and weighing 10-14 kg achieved a mean plasma AUC0-∞ comparable to older children, was highly effective in treating scabies and well tolerated. This study supports extending ivermectin treatment to younger children improving global efforts to control this neglected disease. Funding: Project funding provided by a Thrasher Foundation Early Career Research Award.

Feature-Agnostic Metabolomics for Determining Effective Sub-cytotoxic Doses of Common Pesticides in Human Cells.

While classical molecular biology assays can provide a measure of cellular response to chemical challenges, they rely on a single biological phenomenon to infer a broader measure of cellular metabolic response. These methods do not always afford the necessary sensitivity to answer questions of sub-cytotoxic effects, nor do they work for all cell types. Likewise, boutique assays such as cardiomyocyte beat rate may indirectly measure cellular metabolic response, but they too, are limited to measuring a specific biological phenomenon and are often limited to a single cell type. For these reasons, toxicological researchers need new approaches to determine metabolic changes across various doses in differing cell types, especially within the low-dose regime. The data collected herein demonstrate that LC-MS/MS-based untargeted metabolomics with a feature-agnostic view of the data, combined with a suite of statistical methods including an adapted environmental threshold analysis, provides a versatile, robust, and holistic approach to directly monitoring the overall cellular metabolomic response to pesticides. When employing this method in investigating two different cell types, human cardiomyocytes and neurons, this approach revealed separate sub-cytotoxic metabolomic responses at doses of 0.1 µM and 1 µM of chlorpyrifos and carbaryl. These findings suggest that this agnostic approach to untargeted metabolomics can provide a new tool for determining effective dose by metabolomics (EDm) of chemical challenges, such as pesticides, in a direct measurement of metabolomic response that is not cell type-specific or observable using traditional assays.

Drug and biomarker tissue levels in a randomized presurgical trial on exemestane alternative schedules.

The drug's activity at the target tissue could help to define the minimal effective dose to promote cancer preventive therapy. Here we present exemestane and sex hormone concentrations within breast tissue from a pre-surgical study of alternative exemestane schedules. Postmenopausal women candidate for breast surgery for estrogen receptor-positive breast cancer were randomized to exemestane 25 mg once daily (QD), 25 mg three times/week (TIW), or 25 mg per/week (QW) for 4-6 weeks before surgery. Drug and sex hormones were analyzed from homogenized frozen tissue using a QTRAP 6500+ LC-MS/MS System. Tissue drug concentrations were detectable only in the QD arm with higher concentrations in non-malignant tissue. Estradiol was nearly suppressed in all groups in the non-malignant tissue (QD vs TIW p = .364 and QD vs QW p = .693). In contrast, a dose-response trend was observed in cancer tissue. Based on estradiol suppression in non-malignant tissue, lower exemestane schedules should be explored for breast cancer preventive therapy.

Model-based comparisons of post-treatment free IgE and FEV1 between omalizumab asthma dosing tables in the United States and European Union.

AIMS: Omalizumab is an anti-immunoglobulin E (IgE) monoclonal antibody that was first approved by the United States (US) Food and Drug Administration (FDA) for the treatment of allergic asthma in 2003. The pivotal trials supporting the initial approval of omalizumab used dosing determined by patient's baseline IgE and body weight, with the goal of reducing the mean free IgE level to approximately 25 ng/mL or less. While the underlying parameters supporting the dosing table remained the same, subsequent studies and analyses have resulted in approved alternative versions of the dosing table, including the European Union (EU) asthma dosing table, which differs in weight bands and maximum allowable baseline IgE and omalizumab dose. In this study, we leveraged modelling and simulation approaches to predict and compare the free IgE reduction and forced expiratory volume in 1 second (FEV1) improvement with omalizumab dosing based on the US and EU asthma dosing tables. METHODS: Previously established population pharmacokinetic-IgE and IgE-FEV1 models were used to predict and compare post-treatment free IgE and FEV1 based on the US and EU dosing tables. Clinical trial simulations (with virtual asthma populations) and Monte Carlo simulations were performed to provide both breadth and depth in the comparisons. RESULTS: The US and EU asthma dosing tables were predicted to result in generally comparable free IgE suppression and FEV1 improvement. CONCLUSIONS: Despite the similar free IgE and FEV1 outcomes from simulations, this has not been clinically validated with respect to the registrational endpoint of reduction in annualized asthma exacerbations.

Model-informed precision dosing: State of the art and future perspectives.

Model-informed precision dosing (MIPD) stands as a significant development in personalized medicine to tailor drug dosing to individual patient characteristics. MIPD moves beyond traditional therapeutic drug monitoring (TDM) by integrating mathematical predictions of dosing, and considering patient-specific factors (patient characteristics, drug measurements) as well as different sources of variability. For this purpose, rigorous model qualification is required for the application of MIPD in patients. This review delves into new methods in model selection and validation, also highlighting the role of machine learning in improving MIPD, the utilization of biosensors for real-time monitoring, as well as the potential of models integrating biomarkers for efficacy or toxicity for precision dosing. The clinical evidence of TDM and MIPD is discussed for various medical fields including infection medicine, oncology, transplant medicine, and inflammatory bowel diseases, thereby underscoring the role of pharmacokinetics/pharmacodynamics and specific biomarkers. Further research, particularly randomized clinical trials, is warranted to corroborate the value of MIPD in enhancing patient outcomes and advancing personalized medicine.

Hepatic Metabolic Enzyme Activity with Endogenous Substances-current Status, Challenges and Limitations.

Precision dosing is essential in improving drug efficacy and minimizing adverse reactions, especially in liver impaired patients. However, there is no objective index to directly evaluate the body's ability to metabolize specific drugs. Many factors affect the activity of enzymes, and alter the systemic exposure of substrate drugs, like genetic polymorphism, drug-drug interactions and physiological/pathological state. So, quantifying the activities of enzymes dynamically would be helpful to make precision dosing. Recently, some endogenous substrates of enzymes, such as 6ß-hydroxycortisol (6ß-OH-cortisol)/cortisol and 6ß-hydroxycortisone, have been identified to investigate variations in drug enzymes in humans. Clinical data obtained support their performance as surrogate probes in terms of reflecting the activities of corresponding enzyme. Therefore, a group of Monitored endogenous biomarkers in multiple points can address the uncertainty in drug metabolization in the preclinical phase and have the potential to fulfill precision dosing. This review focuses on recent progress in the contribution of endogenous substances to drug precision dosing, factors that influence enzyme activities, and drug exposure in vivo.

Approach to the child and adolescent with Adrenal Insufficiency.

The management of adrenal insufficiency is challenging, and the overall goals of treatment are to prevent life-threatening adrenal crises, to optimize linear growth, to control androgen levels without overdosing in subjects with congenital adrenal hyperplasia (CAH) and to improve quality of life in affected individuals. Standard glucocorticoid formulations fail to replicate the circadian rhythm of cortisol and control the adrenal androgen production driven by adrenocorticotropic hormone. In order to personalize and tailor glucocorticoid therapy and to improve patient outcomes, new pharmacological strategies have been developed that best mimic physiological cortisol secretion. Novel therapeutic approaches in the management of adrenal insufficiency include new ways to deliver circadian cortisol replacement as well as various adjunctive therapies to reduce androgen production and/or androgen action/effects. Preclinical studies are exploring the role of restorative cell-based therapies, and a first recombinant adeno-associated virus-based gene therapy is also being developed in humans with CAH. In this article, we present three illustrative cases of adrenal insufficiency with different underlying etiologies and times of presentation. Diagnostic and management processes are discussed with emphasis on treatment and outcomes. We have also provided the most up-to-date evidence for the tailored management of children and adolescents with adrenal insufficiency.

Subcutaneous administration of natalizumab can lead to lower drug concentrations compared to intravenous administration.

BACKGROUND: Several studies reported lower drug concentrations with subcutaneous natalizumab compared to intravenous natalizumab. With the emergence of extended interval dosing, gaining more insight into lower concentrations after subcutaneous administration is essential. METHODS: We compared serum trough concentrations between subcutaneous and intravenous administration within a matched cohort (n = 50). RESULTS: Subcutaneous administration (n = 25) was associated with lower concentrations compared to intravenous administration (n = 25) (log-B=-0.28, p = 0.01). In an exploratory group of 11 patients receiving extended interval dosing of subcutaneous natalizumab, the median trough concentration was even lower. CONCLUSION: Subcutaneous natalizumab can lead to lower drug concentrations, potentially limiting extended interval dosing.

Physiologically based pharmacokinetic modeling in obesity: applications and challenges.

INTRODUCTION: Rising global obesity rates pose a threat to people's health. Obesity causes a series of pathophysiologic changes, making the response of patients with obesity to drugs different from that of nonobese, thus affecting the treatment efficacy and even leading to adverse events. Therefore, understanding obesity's effects on pharmacokinetics is essential for the rational use of drugs in patients with obesity. AREAS COVERED: Articles related to physiologically based pharmacokinetic (PBPK) modeling in patients with obesity from inception to October 2023 were searched in PubMed, Embase, Web of Science and the Cochrane Library. This review outlines PBPK modeling applications in exploring factors influencing obesity's effects on pharmacokinetics, guiding clinical drug development and evaluating and optimizing clinical use of drugs in patients with obesity. EXPERT OPINION: Obesity-induced pathophysiologic alterations impact drug pharmacokinetics and drug-drug interactions (DDIs), altering drug exposure. However, there is a lack of universal body size indices or quantitative pharmacology models to predict the optimal for the patients with obesity. Therefore, dosage regimens for patients with obesity must consider individual physiological and biochemical information, and clinically individualize therapeutic drug monitoring for highly variable drugs to ensure effective drug dosing and avoid adverse effects.

Advances in Psychotropic Treatment for Pregnant Women: Efficacy, Adverse Outcomes, and Therapeutic Monitoring.

Advancements in psychotropic therapy for pregnant women are pivotal for addressing maternal mental health during the perinatal period. Screening for mood and anxiety symptoms during pregnancy is recommended to enable early intervention. Psychotropic medications, including antidepressants, benzodiazepines, antipsychotics, and mood stabilizers, are commonly used, but challenges remain regarding their safety and efficacy during pregnancy. Pregnancy induces significant changes in pharmacokinetics, necessitating personalized dosing strategies and careful monitoring. Real-time monitoring technologies, such as smartphone-integrated platforms and home-based monitoring, enhance accessibility and accuracy. Prospective studies and collaboration among healthcare providers are essential for evidence-based guidelines and optimal treatment strategies. Reducing stigma around mental health during pregnancy is crucial to ensure women seek help and discuss treatment options, promoting understanding and acceptance within the community.

Real-world dosing patterns of regorafenib for patients with metastatic colorectal cancer in Spain: the RE-SEARCH study.

PURPOSE: To describe the dosing patterns of regorafenib in a real-world population of patients with metastatic colorectal cancer (mCRC) in a routine clinical practice setting in Spain, focusing on the starting dose of regorafenib. METHODS: An observational, retrospective, multicenter study that included patients ≥ 18 years old who had histologically documented mCRC and who had initiated treatment with regorafenib since January 2017. Post hoc categorization of dosing patterns revealed the following: initial dose < 160 mg and dose escalation, initial dose < 160 mg and maintenance, initial dose equal to 160 mg and maintenance, and initial dose equal to 160 mg and dose reduction. RESULTS: Most patients (152/241, 63.8%) initiated treatment with regorafenib at doses < 160 mg. There was large variation in the starting dose of regorafenib over time: in 2017, most patients (59%) initiated regorafenib at a dose of 160 mg, this proportion decreased to 6% in 2021. There were no significant differences in the median progression-free survival according to the regorafenib dose patterns during the first two cycles. The proportion of patients who reported at least one adverse event (AE), had a grade 3-4 AE or had an AE leading to dose reduction was greater in the group of patients who received an initial dose equal to 160 and reduction. CONCLUSIONS: Our results indicate that physicians in Spain have gradually adopted a dose-escalation approach during cycle 1, which is a common practice for starting treatment with a reduced dose (< 160 mg/day), a strategy that seems to improve tolerability while maintaining efficacy. TRIAL REGISTRATION: Not applicable.