Conditions: Diabetes Mellitus Gout Hyperuricemia
Keywords: SGLT2 SLC5A2 SLC5A4 SLC5A9 SLC2A9 GLUT9 SGLT3 SGLT4 pharmacogenomics
Allocation: NON_RANDOMIZED | Intervention model: SINGLE_GROUP
Enrollment: 30
Healthy volunteers: yes

Brief summary:
Sodium-dependent glucose transporter-2 (SGLT2) inhibitors are a new class of anti-diabetic drugs, which increase urinary glucose excretion thereby promoting weight loss and decreasing plasma glucose levels. We hypothesize that the pharmacodynamic response to SGLT2 inhibitors (specifically canagliflozin) varies among individuals, and that a proportion of this inter-individual variation can be explained by genetic variation. This is a pilot study in healthy, non-diabetic subjects in whom glucose and other related metabolites in the urine and plasma will be measured before and after administration of a single dose of canagliflozin. This will allow us to characterize the inter-individual variation in the pharmacodynamic response to canagliflozin as well as determine if changes in glucose and other related metabolite levels are associated with variants in various candidate genes.

Detailed description:
Sodium-dependent glucose transporters (SGLTs) are a family of glucose transporters expressed on the apical surface of epithelial cells in the intestines and kidneys. Their function is to actively transport glucose across epithelia into the blood. Members of the SGLT-family of transporters include sodium-dependent glucose transporters-1, -2, -3, and -4 (SGLT1, SGLT2, SGLT3 and SGLT4), with SGLT2 being the primary glucose transporter in the kidney. SGLT2 inhibitors are a new class of anti-diabetic drug approved as treatments for type 2 diabetes (T2DM). These drugs inhibit SGLT2-mediated reabsorption of glucose in the renal proximal tubule -- thereby increasing urinary glucose excretion and decreasing plasma glucose levels. We hypothesize that the pharmacodynamic response to SGLT2 inhibitors (specifically canagliflozin) varies among individuals, and that a proportion of this inter-individual variation can be explained by genetic variation. To explore this hypothesis, we will conduct a pilot study in healthy, non-diabetic subjects in whom glucose and other related metabolites in the urine and plasma will be measured before and after administration of a single dose of canagliflozin. This will allow us to characterize the inter-individual variation in the pharmacodynamic response to canagliflozin as well as determine if changes in glucose and other related metabolite levels are associated with variants in candidate genes (SGLT3, SGLT4, and glucose transporter-2 (abbreviated as either GLUT9 or SLC2A9)).

Arms:
arm 1: Research subjects with wild type genotypes at three candidate genes encoding sodium-dependent glucose transporter-3, sodium-dependent glucose transporter-4, and glucose transporter-9 (abbreviated as SLC5A4, SLC5A9, SLC2A9, respectively) will be studied before and after canagliflozin treatment. arm 2: Research subjects who are homozygous for nonsense mutation in SLC5A4 (sodium-dependent glucose transporter-3) will be studied before and after canagliflozin treatment. arm 3: Research subjects who are homozygous for nonsense mutation in SLC5A9 (sodium-dependent glucose transporter-4) will be studied before and after canagliflozin treatment. arm 4: Research subjects who are homozygous for nonsynonymous variant in glucose transporter-9 (SLC2A9) will be studied before and after canagliflozin treatment.

Interventions: intervention 1: Canagliflozin
Intervention descriptions: intervention 1: A single dose of canagliflozin (300 mg, p.o.) will be administered prior to assessing pharmacodynamic response.

Protocol document:
Prot_SAP_000.pdf: 
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Pharmacogenetics of SGLT2 Inhibitors (SGLT2iPGx)  
NCT02462421 
 
 
May 16, 2022 
 
 
 


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Clinical Protocol 
Based on data in a genotype database, a list of individuals was compiled to be invited to 
participate in the clinical trial. Individuals with any of four genotypes were eligible to participate: 
(a) homozygotes for a nonsense mutation in SLC5A4 (rs62239058); (b) homozygotes for a 
nonsense mutation in SLC5A9 (rs850763); (c) homozygotes for a missense variant in SLC2A9 
(rs1689079); and (d) individuals who were homozygous for the “wild type” major alleles of 
SLC5A4, SLC5A9, and SLC2A9. A research nurse accompanied by a liaison (a member of the 
Amish community) made a home visit to invite selected individuals to participate in the study. If 
they expressed interest, the study was explained in detail and potential participants were invited 
to sign a document in which they gave informed consent. Thereafter, the research nurse 
obtained a detailed medical history; measured height, weight and blood pressure; and obtained 
blood samples for screening laboratory tests (hematocrit, fasting plasma glucose, serum 
creatinine, serum sodium, plasma TSH, and HbA1c).  
The clinical trial included two home visits conducted by a research nurse and an Amish liaison: 
1. At the first study visit, the nurse explained the process. Women of reproductive age 
underwent home testing to exclude the possibility that they were pregnant. The research 
nurse obtained baseline blood samples and provided supplies needed for the study 
including a single canagliflozin tablet (300 mg) and supplies necessary for collection of two 
24-hour urine samples. The research participant was instructed to take the canagliflozin 
tablet exactly 24 hours after initiating the first 24-hour urine collection.  
2. The second home visit took place two days after the first visit and 24 hours after the 
participant had taken the canagliflozin tablet. The research nurse obtained blood samples to 
assess pharmacodynamic responses to canagliflozin and collected the two 24-hour urine 
collections. The nurses also obtained information to confirm whether the participant followed 
the instructions and to elicit information about possible adverse events. 
Inclusion/Exclusion Criteria 
Forty individuals were enrolled in this clinical trial between the dates of July 13, 2015 – April 13, 
2016. To be eligible to participate in the clinical trial, individuals were required to be of Amish 
descent, at least 18 years old, and have BMI between 18 – 40 kg/m2. We established the 
following exclusion criteria: 
• 
Known allergy to canagliflozin 
• 
History of diabetes, random glucose >200 mg/dL, or HbA1c >6.5% 
• 
Taking any of the following medications: diuretics, antihypertensive medications, uric acid 
lowering medications, or other medications judged to interfere with interpretation of results 
obtained in the clinical trial. 
• 
Diagnosis of significant chronic diseases affecting the cardiovascular, gastrointestinal, 
pulmonary or renal systems or other diseases judged to interfere with interpretation of 
results obtained in the clinical trial.  
• 
Seizure disorder. 
• 
Pregnancy (self-reported) or breast-feeding within the past three months. 
• 
Estimated glomerular filtration rate < 60 mL/min/1.73 m2 
• 
Hematocrit <35% 
• 
Liver function tests (ALT or AST) greater than two times the upper limit of normal 
• 
TSH outside the normal reference range for the assay. 


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• 
Current symptoms of genitourinary infection or two or more genitourinary infections during 
the prior 12 months. 
• 
History of osteoporosis-associated bone fracture 
• 
History of unhealed foot ulcer 
 
 


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Statistical Analysis Plan 
This study was designed as an open-label clinical trial with four arms based on the participants’ 
genotypes. Based on our power calculations, we aimed to study a total of 110 individuals:  
• 
20 homozygotes for the nonsense mutation in SLC5A4 (rs62239058; p.E139X) 
• 
20 homozygotes for the nonsense mutation in SLC5A9 (rs850763; p.E593X) 
• 
25 homozygotes for the missense variant in SLC2A9 (rs1689079; p.V253I) 
• 
45 “control” individuals who were homozygous for the major alleles of all three genes. 
The clinical trial was terminated early when it became apparent that we would not succeed at 
meeting our recruitment targets within the available time and budget. Thirty individuals 
completed the study: 
• 
4 homozygotes for the nonsense mutation in SLC5A4 (rs62239058; p.E139X) 
• 
6 homozygotes for the nonsense mutation in SLC5A9 (rs850763; p.E593X) 
• 
7 homozygotes for the missense variant in SLC2A9 (rs1689079; p.V253I) 
• 
13 “control” individuals who were homozygous for the major alleles of all three genes. 
Primary Outcomes 
We defined two primary outcomes based on biomarkers for efficacy: 
(a) Glycemic efficacy (drug-induced glucosuria expressed as grams of glucose per gram of 
creatinine). The outcome data were based on the second 24-hour urine sample collected 
after the participants received canagliflozin. (Healthy participants excrete negligible 
quantities of glucose in urine at baseline prior to receiving an SGLT2 inhibitor.)  We 
analyzed data using unpaired t-tests comparing data from each of the groups of 
homozygotes for the three genetic variants versus the control group. We did not correct for 
multiple comparisons in light of the decision to terminate the study early before achieving 
our recruitment targets. We have reported nominal two-sided p-values. 
(b) Uricosuric efficacy (drug-induced increase in fractional excretion of uric acid). Fractional 
excretion of uric acid was calculated as: 
[(urinary uric acid) x (serum creatinine)] ÷ [(urinary creatinine) x (serum creatinine)] 
The effect of canagliflozin was calculated as the difference between fractional excretion of 
uric acid after receiving canagliflozin minus the fractional excretion of uric acid at baseline. 
We analyzed data using unpaired t-tests comparing data from each of the groups of 
homozygotes for the three genetic variants versus the control group. We did not correct for 
multiple comparisons in light of the decision to terminate the study early before achieving 
our recruitment targets. We have reported nominal two-sided p-values. 
 
Secondary Outcomes 
We defined four secondary outcomes based on biomarkers for efficacy.  We analyzed data 
using unpaired t-tests comparing data from each of the groups of homozygotes for the three 
genetic variants versus the control group. We did not correct for multiple comparisons in light of 
the decision to terminate the study early before achieving our recruitment targets. We have 
reported nominal two-sided p-values. 
(a) Natriuresis (drug-induced urinary sodium excretion expressed as percentage increase in 
sodium excretion in response to canagliflozin). The outcome data were based on 
comparisons of urinary sodium excretion in response to canagliflozin divided by urinary 
sodium excretion of sodium at baseline.  


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(b) Serum levels of metabolites (fasting plasma glucose, serum creatinine, and serum uric acid 
levels expressed as mg/dL). The outcome data were calculated as the absolute difference 
between serum levels after receiving canagliflozin minus serum levels at baseline.