This study will aim to determine whether treatment with the SGLT2 inhibitor luseogliflozin (which has high SGLT2 selectivity) affects bone metabolism by assessing the changes in bone microstructure using second-generation HR-pQCT in elderly patients with T2DM.
This is a pilot trial to assess the effect of SGLT2 inhibitors on bone metabolism. We designed a single-center, randomized, open-label, parallel-group, active-controlled trial for patients with T2DM whose conditions have never been complicated with osteoporosis. We will randomly assigned 24 patients into 1:1 ratio to the luseogliflozin group (receiving additional treatment with luseogliflozin) or the control group (receiving additional treatment with metformin). The study follow-up duration is 48 weeks. The study will be conducted at Nagasaki University Hospital, Japan. The study design is summarized in Figure 1.
The primary outcome measures are changes in the predicted bone strength as determined by second-generation HR-pQCT, evaluated using the parameters of (1) bone stiffness, and (2) the estimated failure load of the radius and tibia of the nondominant body side. For each parameter, any change will be determined based on the difference between the measurement results at baseline (week 0) and week 48.
The study's secondary outcome measures are as follows. (1) The changes in the structures of cortical bone, trabecular bone, and the bone morphology measured by HR-pQCT as described below in the 'Image measurements' section from baseline (week 0) to week 48. (2) The changes in the laboratory data values, including the levels of glycated hemoglobin (HbA1c) from week 0 to weeks 12, 24, 36 and 48. (3) The changes in the areal BMD of the lumbar spine (L1–L4), femoral neck, and distal radius estimated by DXA from week 0 to week 48. (4) The incidence of vertebral fracture or femoral fracture from week 0 to week 48. (5) Changes in the bone metabolic markers from week 0 to week 48.
In addition to the primary and secondary outcomes, we will evaluate adverse effects from both luseogliflozin and metformin (control agent). We will also evaluate the recruitment rate and consent rate.
Sample size estimation
This is a pilot trial to assess the changes in bone microstructure affected by luseogliflozin treatment compared with metformin treatment, evaluated by HR-pQCT. There is no prior similar study comparing the bone strength before and after intervention that can be used to estimate the precise optimal sample size. Julious et al. reported that 12 participants per group are needed for a pilot study (22). The justification for this sample size is based on the rationale concerning feasibility and precision regarding the mean and variance of the primary outcome measures.
Patients and public involvement statement
There is no patient or public involved in this trial.
Participants and recruitment
A total of 24 participants aged ≥60 years will be recruited into the study. The enrollment started in June 2019. All participants have been diagnosed with T2DM, and their cases have never been complicated with osteoporosis. Patients fulfilling the inclusion criteria described below will be invited to a screening for their eligibility. Principal investigator and co-investigators recruit the participants among their outpatients, and obtain a written informed consent from the participants. There are no additional consent provisions for collection and use of participant data and biological specimens in ancillary studies. The recruitment rate and the consent rate will be evaluated at the end of the study.
As shown in Figure1, participants must fulfill the following criteria to be eligible for inclusion at their first visit to Nagasaki University Hospital (visit 1): (1) an individual aged ≥60 years; (2) diagnosed with T2DM; (3) an outpatient; (4) treated with diet therapy alone or with oral antidiabetic agents including metformin (≤1000 mg per day), and/or an alpha-glucosidase inhibitor (α-GI) and/or a dipeptidyl peptidase-4 (DPP-4) inhibitor, whose treatment has not been changed within 6 months before enrollment; and (6) providing written informed consent.
Participants will be included when they also fulfill the following criteria at week 0 (visit2): (1) the patient's HbA1c (NGSP) level is ≥7.0% and <9.0%; (2) the patient's T-score in both lumbar vertebrae and the femoral neck determined by DXA is > −2.5 standard deviations (SD).
Eligible participants will be excluded if they meet any of the following criteria: (1) a previous history of treatment with an SGLT2 inhibitor; (2) complicated with a bone metabolic disorder (i.e., osteomalacia, thyroid dysfunction, hyperparathyroidism, or hypoparathyroidism which requires any medical treatments) (3) administered any treatment for osteoporosis within 12 months before enrollment (e.g., a bisphosphonate, vitamin D preparation, vitamin K preparation, calcium preparation, selective estrogen receptor modulator, antireceptor activator of nuclear factor kappa-Β ligand antibody [denosumab], anti-sclerostin antibody [romosozumab], or recombinant human PTH [teriparatide]); (4) treated with estrogen or testosterone hormone replacement therapy; (5) complicated with diabetic retinopathy and/or diabetic neuropathy that required therapeutic intervention; (6) severe renal dysfunction defined as an estimated glomerular filtration rate (eGFR) <30 mL/min/1.73 m2; (7) severe anemia (Hb <10 g/dL); (8) complicated with malignancy; (9) hypersensitivity or allergy to metformin and/or luseogliflozin; (10) alcohol consumption >20 g/day; (11) a smoking habit, including smoking even one cigarette per day, within 12 months before enrollment; (12) participating in other clinical research within 6 months before enrollment; (13) complicated with chronic liver disease with ≥6 points as the Child-Pugh score; (14) body mass index (BMI) <18.5 kg/m2; (15) otherwise deemed inappropriate by the study's principal investigator.
Participants will be withdrawn from this trial after randomization if they meet any of the following criteria: (1) exhibiting an increase in the HbA1c level that is ≥0.5% of the baseline (week 0) for any two successive visits; (2) an HbA1c level >10.0% at any visit; (3) the occurrence of any adverse event that is ≥grade 3 of the Common Terminology Criteria for Adverse Events (CTCAE) ver. 4.0; (4) showing any fracture(s) with the exception of an occult fracture; (5) has requested withdrawal from the study; (6) has requested a change or the discontinuation of the diabetes treatment; (7) it is determined that it is inappropriate for the patient to continue the study by the investigators because of the progression of an underlying disease or a complication, or the occurrence of unidentified disease; (8) it is judged by the investigators that it is inappropriate for the patient to continue participating in the study for any other reason.
This protocol was approved by Clinical Research Review Board of Nagasaki University which is certified by Japan's Ministry of Health, Labour and Welfare (approval no. CRB18-0006). The study is registered on the University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR) as UMIN-CTR no. 000036202. The study is conducted in accordance with the 7th revision of the Declaration of Helsinki 2013 and the Clinical Trials Act enforced in April 2018 in Japan.
Setting and study timeline
All participants are recruited at Nagasaki University Hospital. Each participant’s information as listed below is collected at the prescreening for enrollment (visit 1); age, sex, height, comorbid complications, diabetes duration, history of diabetes treatment, family history of diabetes and osteoporosis within the second degree of kinship, and histories of smoking, drinking, and fracture. Body weight, blood pressure, and pulse rate in a sedentary position are measured at every visit of the study (at visits 1–6, and [if withdrawing from the study] at withdrawal). As shown in Table 1, the participants will undergo examinations by spine X-ray, DXA, and HR-pQCT at week 0 (visit 2) and week 48 (visit 6). When participants need to be withdrawn from the study for any reason, they will undergo HR-pQCT within 4 weeks after discontinuing the study drug. Blood specimens are obtained at every visit except the prescreening visit (visit 1).
Frontal and lateral X-ray examinations are performed to detect compression fractures of thoracic and lumber vertebrae using a semiquantitative technique.(23) DXA is performed for the assessment of the areal BMD at the lumbar spine (L1, L2, L3, L4, L1–4, L-min), total hip (right total, left total), femoral neck (rt. neck, lt. neck), and 1/3 distal of the radius (rt. radius, lt. radius) using DXA system (iDXA, GE Medical Systems, WI, USA). The second-generation HR-pQCT (Xtreme CT II, Scanco Medical, Brüttisellen, Switzerland) scans the radius and tibia of the nondominant body side to evaluate the bone microstructure.
We measure the following parameters by HR-pQCT: (1) bone density, i.e., total volumetric bone mineral density, trabecular volumetric bone mineral density, and cortical volumetric bone mineral density, (2) trabecular bone parameters, i.e., bone volume fraction, trabecular thickness, trabecular number, and trabecular separation, (3) cortical bone parameters, i.e., cortical thickness, cortical porosity, and cortical pore diameter, (4) bone morphology, i.e., total area, trabecular area, cortical area, and periosteal perimeter, and (5) predicted bone strength, i.e., stiffness and failure load.
At visits 3–5, we measure the patients' complete blood count and plasma levels of sodium, potassium, chlorine, calcium, phosphate, magnesium, total protein, albumin, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglyceride, blood urea nitrogen, creatinine, total bilirubin, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, alkaline phosphatase, γ-glutamyl transpeptidase, creatine kinase, uric acid, glucose, and HbA1c. At visit 2 and visit 6 (and at withdrawal if discontinuing participation), in addition to the above laboratory data, we measure the serum (plasma) levels of glycoalbumin, C-peptide, glucagon, glutamic acid decarboxylase antibody, intact parathyroid hormone (PTH), whole PTH, free thyroxine, thyroid-stimulating hormone, adrenocorticotropic hormone, luteinizing hormone, follicle-stimulating hormone, total estradiol, total testosterone, sex hormone-binding globulin, total cortisol, growth hormone, insulin-like growth factor-1, homocysteine, glucagon, tartrate-resistant acid phosphatase 5b, total type Ⅰ procollagen N-terminal propeptide, bone-specific alkaline phosphatase, undercarboxylated osteocalcin, osteocalcin, 25-hydroxyvitamin D, 1,25-dihydroxyviamin D, sclerostin, dickkopf-1, and pentosidine. There are no plans for collection, laboratory evaluation, and storage of biological specimens for genetic or molecular analysis in the current trial and for future use in ancillary studies.
Randomization and allocation concealment
A randomized, open-label, parallel pilot trial design has been set up. On the day on which the first administration of the study drug (visit 2) is planned after the eligibility assessment, each participant is sequentially allocated to either the luseogliflozin group or the control group in a 1:1 ratio, using a blocked randomization stratified by sex (female or male). The allocation is conducted by the participant-registration center, and the result is sent to the investigators via facsimile so that the block size. As the study design is open label with only outcome assessors being blinded, unblinding will not occur during the study.
(1) Luseogliflozin group: Participants allocated to the luseogliflozin group will take oral luseogliflozin (Taisho Pharma Co., Tokyo) at 2.5 mg/day from the beginning of the trial (visit 2) in addition to their previous treatment. The dose of luseogliflozin will be increased to 5 mg from visit 3 unless a participant achieves an HbA1c level <7% or a decrease in the HbA1c of ≥0.5% compared to the previous visit. The maximum dose of luseogliflozin permitted is up to 5 mg/day. If a participant cannot achieve the HbA1c levels described above with 5-mg luseogliflozin, an additional treatment with metformin (Sumitomo Dainippon Pharma Co., Osaka, Japan) will be prescribed at each visit by 500-mg increments up to 1500 mg. The daily dose of metformin will be increased by 250 mg at each visit if the participant already takes ≥1500 mg/day. The maximum dose of metformin permitted is 2250 mg/day.
(2) Control group (Metformin group): Participants allocated to the control group will be newly administered or added oral metformin 500 mg/day from the beginning of the trial (visit 2) in addition to the previous treatment. The additional metformin will be administered at each visit by 500-mg increments unless the participant achieves an HbA1c level <7% or a decrease in HbA1c ≥0.5% compared to the previous visit. The daily dose of metformin will be increased by a 250-mg increment at each visit if the participant already takes ≥1500 mg/day. The maximum dose of metformin permitted is 2250 mg/day.
Adverse events (AEs)
All adverse events (AEs) that occur during the trial will be recorded on a case report form and reviewed as part of the central data monitoring. Investigators explain AEs to the participants and offer appropriate care. If serious AEs such as death, a life-threatening condition, hospitalization, sequelae, disability, and congenital illness occur during the trial, the principal investigator will report the AE to the Minister of Health, Labour and Welfare (Japan) and the certified review board within 15 days.
Data collection, data management and monitoring
All the data will be collected using the research electronic data capture (REDCap) system by the authorized investigators. Once the data are checked, they will be fixed by the trial steering committee (TSC). The TSC provides overall supervision for the trial on behalf of the sponsor and funder and to ensure that the trial is conducted to the rigorous standards set out in the guideline of the Clinical Trials Act. The meeting of the TSC will be held every month over the course of the trial to oversee conduct and progress. Clinical Porter Inc. (Tokyo), a site management organization (SMO) specializes in clinical trial management which is independent from the sponsor and competing interest, will monitor the overall conduct of the trial, safeguarding the interests of the trial participants and assessing the safety and efficacy of the intervention. The authorized person of the SMO visits before and every year after starting the trial to review protocol compliance, conduct source data verification, assess laboratory procedure, and ensure that the study is being conducted in accordance with protocol requirement. Because the risk of intervention in the trial is considered to be extremely low, a regular audit is not conducted in the trial unless serious concerns about the outcomes or/and serious AEs arise. Once a serious event occurred, the authorized persons of the Clinical Research Support Center of Ryukyu University Hospital, which is independent from the investigators and the sponsor; will make a site visit to audit the trial conduct. The sponsor is responsible for all aspects of local organization including identifying potential recruits and taking consent.
As stated above in the Objectives section, the primary outcome of this study is the extent of luseogliflozin's effects on bone quality change. Hence, the primary data analysis will be conducted using the set of participants with sufficient exposure to the allocated drugs. For this reason, we will use a per protocol set (PPS), the definition of which includes the adherence ratio, as the target population in the primary data analysis. The same analyses will be conducted on a full analysis set (FAS) modified FAS (mFAS) to provide supplemental information about the influence of selecting PPS subjects on the results.
As the primary and the secondary data analyses, the adjusted mean and the 95% confidence intervals (95%CI) of the bone deterioration effect of the treatment group will be estimated as regression coefficient and its standard error for the respective primary and secondary outcome measures, under a linear regression model with the following two covariates: the baseline measurement of the respective measures and the stratification factor in the randomization (i.e., sex). This study is set up as a pilot study, but we will test the null hypotheses that "the mean of the bone quality deterioration effect of the treatment group is 0" by determining whether the 95%CIs contain the null hypotheses.
The respective analysis sets are defined as follows. The intention to treat (ITT) population is defined as all participants registered for this trial; the safety analysis set (SAS) population is defined as the participants in the ITT population with at least one administration of luseogliflozin/metformin. The full analysis set (FAS) population is defined as the participants in the SAS for whom data about the predicted bone strength after the administration of luseogliflozin/metformin at one or more scheduled visits are available. The PPS is defined as the participants in the FAS with the primary outcome measure. Other criteria for the PPS will be determined before the database lock of this study. We defined the modified FAS (mFAS), the definition of which is a relaxed version of PPS by allowing missingness of the data of predicted bone strength at week 48 only if the data of the items at withdrawal from this study are obtained.
As a safety analysis, tabular summaries of AE incidence among subjects in a SAS will be created. All hypothesis testing will be conducted at the significance level of 0.05 (two-sided). The data collected will be summarized using the arithmetic mean, the standard deviation, and the quantiles. All statistical analyses are conducted under the computing environment R. (R Foundation for Statistical Computing, Vienna, Austria)