The study is a multi-center, open-label, non-randomized, exploratory, prospective, interventional study (Figure 1). The subjects are stratified into two groups based on the ratio of basal insulin (Basal) to the total daily insulin dose (TDD) (Basal/TDD, < 0.4 or >, 0.4). Instructions to the study subjects are found in Table 1.
A pre-observation period of 4 weeks is set before the intervention (administration of SGLT2 inhibitor). During this period, study subjects will measure and record fasting plasma beta-hydroxybutyric acid (BOHB), flash glucose monitoring (FGM), and self-monitoring of blood glucose (SMBG). The start of SGLT2 inhibitor administration is set as day zero of the observation period. The study subjects will visit the research institutions 4 times; at weeks -4, 0, 2, and 4. The study subjects were given a digital camera and instructed to take a picture of each meal they eat throughout the observation period.
[Group A] Study subjects reduce basal insulin dose by 0% (instructed to reduce bolus insulin dose)
Subjects whose Basal/TDD ratio is < 0.4 are instructed not to reduce basal insulin dose but to reduce bolus insulin dose by 10%. The 10% reduction of the bolus insulin dose is based on 90% carbohydrate insulin ratio (CIR), and is rounded to the nearest whole number in case of insulin therapy with multiple daily injections (MDI), or rounded down to two decimal places in case of continuous subcutaneous insulin infusion (CSII). The study subjects are instructed to follow this instruction for 3 days from the start of the intervention. After the fourth day, subjects can titrate both basal and bolus dose according to “Algorithm for Basal Insulin Titration after SGLT2 administration (Figure 2)” and “Algorithm for Bolus Insulin Titration after SGLT2 administration (Figure 3).”
[Group B] The study subjects are instructed to reduce basal insulin by 10%
Study subjects whose Basal/TDD is >0.4 are instructed to reduce total insulin dose by 10%, reducing the basal insulin dose only. The dose of basal insulin is rounded down to one decimal places in case of MDI or to two decimal places in case of CSII. The study subjects are instructed to follow this instruction for 3 days from the start of the intervention. After the fourth day, subjects can titrate both basal and bolus dose according to “Algorithm for Basal Insulin Titration after SGLT2 administration (Figure 2)” and “Algorithm for Bolus Insulin Titration after SGLT2 administration (Figure 3).”
In line with the objectives of the study and for ensuring the safety of the subjects, the inclusion and exclusion criteria explicated in table 2 were set. In order to appropriately evaluate the efficacy of the study drugs, patients who require a legal representative are excluded.
Observations and the schedule are shown in table 3 and table 4. In principle, the study subjects will visit the research institutions, and at every visit, blood tests (fasting) and urine tests (spot) is performed. Investigators collect and enter the results of examinations listed in table 3 in the case report form (CRF), and send the CRF to the data center. Adverse events are followed as safety endpoints throughout the study. The items which the study subjects themselves measure are recorded onto the specific documents and sent to the data center via the investigators.
Data management and monitoring
Data collection and management are carried out by third-party entities to avoid bias. The data management is performed by Soiken Inc. Data Management Group (the Data Centre). The Data Centre prepared a procedure manual for data management. The Data Centre’s approval is required prior to sending any data related to the subjects in an electronic format. If data is transmitted over an unsecured electronic network, the data must be encoded at the source. Linkable anonymization by central registration number is used to identify the subjects. The investigators are responsible for appropriate storage of the correspondence table prepared by them to identify the subjects, in accordance with the procedures at the particular research institution. This correspondence table will be retained for 5 years after the completion of this study. Appropriate measures such as encoding or deletion are taken to ensure that the subjects cannot be identified, in accordance with applicable laws and regulations.
The Data Centre monitors this study to manage and ensure quality. The monitoring manager monitors the subjects in accordance with the prescribed manual on monitoring. For data quality management, the principal investigator and Central Committee confirms the progress of this study as necessary through the Data Centre to ensure conformance with the protocol and the Ethical Guidelines for Medical and Health Research Involving Human Subjects (28 February 2017; Ministry of Education, Culture, Sports, Science and Technology/Ministry of Health, Labor and Welfare) and the Clinical Trials Act (14 April 2017; Ministry of Education, Culture, Sports, Science and Technology/Ministry of Health, Labor and Welfare).
Frequency of hypoglycemia per day confirmed by self-monitoring of blood glucose (SMBG) during the intervention period (administration of SGLT2 inhibitor) (number of hypoglycemia/day).
- Frequency of ketosis before and after the intervention
Ketosis is defined as plasma BOHB ≧ 600 μmol/L [11–12]. Frequency of ketosis is defined as the proportion of the number of days in which ketosis occurs in the study subjects during the pre-observation period and the observation period after the intervention.
- Frequency of hypoglycemia per day before and after the intervention detected by FGM (number of hypoglycemia/day)
- Change and difference in change between the intervention groups on the following items, before and after the intervention
3-1. Fasting plasma beta-hydroxybutyric acid (ketone body)
3-2. Basal insulin dose*, bolus insulin dose*, total insulin dose*, Carbohydrate Insulin Ratio (CIR), and Insulin Sensitivity Factor (ISF)
3-3. Time spent in hypoglycemia (percentage of time spent in glucose range ≦ 70 mg/dl), time in hyperglycemia (percentage of time spent in glucose range ≧ 70 mg/dl) time spent with nocturnal hypoglycemia, detected by FGM
3-4. Vital signs: blood pressure, pulse rate
3-5. Body weight, BMI, skeletal muscle mass†, fat mass†
3-6. Blood biomarkers: red blood cell count, white blood cell count, hemoglobin, hematocrit, blood platelet count, hepatic enzymes (AST, ALT, LDH, ALP, gamma-GTP), UA, T-Chol, HDL, LDL, TG, BUN, Cre, eGFR, BNP†, HbA1c (or glycoalbumin), plasma glucose, albumin, CPR†, and CPR index†
3-7. Urine biomarker: specific gravity, pH, protein, glucose, ketone body, occult blood, urobilinogen, bilirubin, microalbumin, creatinine, and microalbumin-creatinine ratio
3-8. Total ketone body†, beta-hydroxybutyric acid†, and acetoacetic acid†
3-9. QOL score (DTSQ)
*measured by daily dose, †measured at visit 2 and 4 only
Frequency of adverse events (including frequency of hypoglycemia detected by FGM)
Correlation between change in dietary habit, dietary content, and nutrient intake and change in fasting plasma beta-hydroxybutyric acid.
Change in plasma microRNA profile.
Change in cardiac function estimated by ultrasonic echocardiography (UCG).
Rationale underlying the sample size
This study is designed as an exploratory study, and no prior studies have reported the frequency of hypoglycemia after the administration of SGLT2 inhibitor. We hypothesized that the frequency of hypoglycemia per day would increase after the administration of SGLT2 inhibitor, if the dose of basal insulin was not titrated. The frequency of hypoglycemia has been reported to be 7 ± 6 times/month when insulin glargine is used in patients with TIDM . The assumed increased hypoglycemia, and the required sample sizes are plotted in figure 4. When 26 patients were in one group, the % increase in hypoglycemia was more than 60%, which was deemed adequate. With an estimated dropout rate of 10%, the planned number of subjects (60 subjects, 30 in each group) is thought to have enough statistical power for an increased hypoglycemia frequency of more than 60% (11.2 ± 6 times/month) in Group A (Basal/TDD is < 0.4, the study subjects are instructed to reduce basal insulin dose 0% but instructed to reduce bolus insulin dose 10%) from 7 ± 6 times/month in Group B (Basal/TDD is 0.4 or higher, the study subjects are instructed to reduce basal insulin 10%).
This study is being conducted at 7 research institutions where a total of 350 patients with T1DM are being treated. From a previous survey, 30% of these patients are eligible to use SGLT2 inhibitors as per the Japanese labelled indications, meaning that approximately 100 patients could potentially use the SGLT2 inhibitor with insulin. Among the 100 patients, all patients who sign a written consent form are enrolled in the study, and stratified into Group A (Basal/TDD is < 0.4, subjects instructed to reduce basal insulin dose 0% and bolus insulin dose by 10%) or Group B (Basal/TDD >0.4, subjects instructed to reduce basal insulin by 10%). The proportion of patients who will consent is assumed to be 80%, and the proportion of patients who meet the inclusion criteria and none of the exclusion criteria is assumed to be 80%. Under these conditions, the target number of 60 study subjects is feasible.
Basic analytical procedure
For primary and secondary endpoints, both full analysis set (FAS) and per protocol set (PPS) will be analyzed. The analyses will be conducted with a two-sided significance level of 5%. A biomedical statistic expert created a statistical analysis plan (SAP) separately, and specified the details of the statistical methods including handling data. The SAP was prepared before the database lock.
When amendment of the SAP is needed, the data handling committee will carefully consider the effect of the amendment on the study itself, the results of the study, the ethical concerns and scientific validity of the effect. If the data handling committee judges that the amendment of the SAP is valid, the procedure, the content, and the result of the discussion is recorded.
Analysis of study subjects’ background information
Summary statistics will be calculated for background information of study subjects per group. Frequencies and percentages of categories are shown for nominal variables. Summary statistics (number of cases, mean, standard deviation, minimum, median, and maximum values) will be calculated for continuous variables. For comparisons between the groups, Chi-square test will be used for nominal variables. If the proportion of the cells with expected frequency of less than 5 is 20% or more, Fisher’s exact test will be used. For comparisons between groups for continuous variables, two-sample t-test or Wilcoxon rank sum test is used.
Analysis of the primary endpoint
Summary statistics will be calculated for the number of hypoglycemic events per day (plasma glucose level defined by SMBG <70 mg/dL) during the intervention period (from baseline to week 4) using FAS as main analysis set and PPS for sensibility analysis set. For comparisons between groups, two-sample t-test and analysis of covariance will be conducted, and differences between the groups and their 95% confidence intervals calculated. HbA1c, age, and frequency of hypoglycemia (<70 mg/dL, confirmed by SMBG) per day during the pre-observation period before the intervention (week -4 to baseline) will be used as covariates in the analysis of covariance. If the data distribution does not follow a normal distribution, summary statistics will be calculated after logarithmic transformation.
Analysis of the secondary endpoints
For the analysis of the secondary endpoint 1 (frequency of ketosis) and 2 (frequency of hypoglycemia detected by FGM), summary statistics of measurements and changes will be calculated using FAS during the pre-observation period before the intervention (week -4 to baseline) and the observation period after the intervention (baseline to week 4) in each group. For the measurements, two-sample t-test will be used for comparisons between groups, and for the change, one-sample t-test will be used for comparison in each group. If the data distribution does not follow a normal distribution, summary statistics will be calculated after logarithmic transformation.
For the analysis of the secondary endpoint 3, summary statistics will be calculated using FAS for measurements at each observation point and change in the measurements from baseline to each observation point after the intervention. For the measurement, two-sample t-test will be used for comparisons between groups, and for the change in the measurement, one-sample t-test will be used for comparison in each group.
Analysis of the safety endpoints
For the analysis of the safety endpoints, a table of all adverse events and diseases or the like will be created for each group using the safety analysis set, and comparisons performed between groups as necessary using Fisher’s exact test.
Analysis of exploratory endpoints
For the analysis or correlation between change in dietary habit, dietary content, and nutrient intake and change in fasting plasma BOHB acid, Spearman rank correlation coefficient and its 95% confidence interval will be calculated, and evaluated for significance. The subjects have been instructed to take pictures of each of their meals using digital camera. The stored images will be uploaded to a cloud, and diabetologists will analyze the images according to the Standard Tables of Food Composition in Japan using a specialized application (Asken, Wit Co., Ltd.). The volumes and calories of carbohydrates, proteins, fats, and nutrient intakes will be calculated by the system referred to as “online nutritional evaluation.”
Ethics and Dissemination
The protocol was approved by Kyoto Prefectural University of Medicine, Clinical Research Review Board (CRB5180001), and registered at jRCT (jRCTs051190114).
The findings will provide knowledge about the reduction of the basal insulin dose combined with an SGLT2 inhibitor in patients with T1DM, which may reduce the frequency of hypoglycemia associated with the combination therapy. The results will be disseminated through presentations at appropriate conferences and meetings, and publications in peer-reviewed journals.
All parties involved in this study will endeavor to protect the personal information of study subjects. This study is being conducted in accordance with the Personal Information Protection Law, and other legislation/law and regulations. Unique information (initial, carte number) of study subjects is stored securely in the research institutions, and information that allows a person outside the research institution to identify the study subjects (such as name, address, telephone number, etc.) is not included in CRFs and registration database.
A central registration number is used when the data center enquires regarding data from a study subject at a research institution. Investigators use the correspondence tables to identify their research subjects (anonymization), which are managed by themselves. Investigators store the correspondence tables securely and keep them properly until at least 5 years from the day of the completion of the study. The person responsible for personal information management at each research institution shall be the responsible investigator unless otherwise specified.
The principal investigator, the responsible investigators, sub-investigators, and the heads of the research institutions agree to store the study-related information properly until at least 5 years from the completion date of the study. The responsible person in charge of data management also stores the study-related information such as CRF as source documents and electronic information, such as data sets, are properly stored in the same way.
After the storage period, the data is to be discarded. Anonymized data collected for the analysis is kept stored for future secondary study such as meta-analysis. If the anonymized data is used for other studies, approval from the ethics review board is required before study implementation.
Samples for special blood tests are measured in laboratories utilized by each research institution. After the requisite data is obtained, the samples are disposed of, in accordance with standard procedural guidelines.
The study explores whether the reduction of the basal insulin dose combined with SGLT2 inhibitor in patients with type 1 diabetes mellitus can reduce the frequency of hypoglycemia with an overall acceptable safety profile.
The treatment intervention in this study is based on the Basal/TDD at consent. Therefore, the study subjects cannot always receive their desired treatment. However, all study subjects will receive regular medication, and will measure ketone body and blood glucose, and titrate both basal and bolus insulin after the fourth day of the intervention. As a result, the study subjects may receive better medical care than would be the case if they did not participate in this study.
To reduce the burden on study subjects, the change of medications during the study are not restricted. Special blood tests are conducted using the residual samples to reduce the burden caused by multiple blood draws. Therefore, generally, special compensation is not provided even when health damages are considered to be caused by the drug(s) used in the study. For reporting purposes, all incidences during the study will be treated similarly to health damage or medical accidents caused by regular medication. The compensation in such a case is based on the Adverse Drug Reaction Relief System of the Pharmaceutical and Medical Devices Agency, Product Liability Law, or product liability insurance. The principle investigator contracted the insurance for clinical study corresponding to any incidences. The current research is carried out in accordance with the Clinical Trial Act and other laws and regulations. Burdens and predicted risks are minimized as much as possible from the perspective of protecting human subjects. In particular, we believe that the risk of adverse effects can be minimized by discontinuing the study treatment as soon as a symptom emerges and providing treatments using appropriate procedures. Based on the overall evaluation, and taking into account conceivable benefits from the study participation, this study protocol is considered appropriate to implement and adequate in terms of ethical considerations.