TITLE: Combination therapy with sitagliptin and lansoprazole in patients with recent-onset type 1 diabetes (REPAIR-T1D): 12-month results of a multicentre, randomised, placebo-controlled, phase 2 trial

  ABSTRACT.SUMMARY.BACKGROUND:
Type 1 diabetes results from autoimmune destruction of pancreatic β cells. Findings from preclinical studies suggest that dipeptidyl peptidase-4 inhibitors and proton-pump inhibitors might enhance β-cell survival and regeneration. We postulated that sitagliptin and lansoprazole would preserve β-cell function in patients with recent-onset type 1 diabetes.

ABSTRACT.SUMMARY.METHODS:
We did a double-blind, placebo-controlled, phase 2 trial (REPAIR-T1D). Participants aged 11–36 years, diagnosed with type 1 diabetes within the past 6 months were recruited from Sanford Health Systems (Sioux Falls, SD, USA; Fargo, ND, USA), Children's Hospitals and Clinics of Minnesota (St Paul, MN, USA), and Rady Children's Hospital (San Diego, CA, USA). Participants were randomly assigned (2:1) to receive oral sitagliptin (100 mg for participants ≥18 years, 50 mg for those <18 years) and lansoprazole (60 mg for participants ≥18 years, 30 mg for those <18 years) or matched placebo for 12 months. Randomisation was done by a blocked randomisation process (blocks of three and six), with separate streams for younger (<18 years) and older (≥18 years) participants, and males and females. All participants and personnel remained masked until after the completion of the final 12 month visit, at which time data were unmasked to the analysis team. The primary endpoint was C-peptide response to a mixed meal challenge at 12 months measured as 2 h area under curve. Analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT01155284.

ABSTRACT.SUMMARY.FINDINGS:
Between Sept 21, 2010, and May 29, 2012, 46 participants were randomly assigned to the treatment group and 22 to the placebo group; of whom 40 participants in the treatment group and 18 in the placebo group completed the 12-month treatment. At 12 months, the mean change in C-peptide area under curve was −229 pmol/L (95% CI −316 to −142) for the treatment group and −253 pmol/L (−383 to −123) for the placebo group; this difference was not significant (p=0·77). No adverse or serious adverse events were probably or definitely related to the study treatment.

ABSTRACT.SUMMARY.INTERPRETATION:
Although the expected change in the primary endpoint was not achieved, not all participants had increases in glucagon-like peptide-1 and gastrin concentrations that were expected with treatment. Although participants did not have adverse events related to study drugs, the study is not powered to address safety definitively. Further trials including these drugs might be warranted, but should be designed to ensure appropriate selection of participants and increases in these intermediary hormones.

ABSTRACT.SUMMARY.FUNDING:
Sanford Research and JDRF.

BODY.INTRODUCTION:
Type 1 diabetes is an autoimmune disorder targeting pancreatic β cells that secrete insulin.1 It is one of the most common chronic diseases of children, and the incidence is increasing worldwide.2 For a time after diagnosis, some β-cell function remains, although not enough to maintain euglycaemia. In this context, even slight protection of residual β-cell function can be expected to have clinically significant benefits.3  Although insulin is life-saving, no treatment is available to address the underlying disease process. Various immune therapies have been shown to slow the progressive loss of pancreatic islet β-cell function and insulin secretion after disease onset in type 1 diabetes.4–11 Unfortunately, none of these immunomodulatory drugs have induced lasting disease remission.  We have shown that combination therapy with the gastrointestinal hormones glucagon-like peptide-1 (GLP-1) and gastrin increased β-cell mass and restored normoglycaemia in non-obese diabetic (NOD) mice.12 Combination therapy with a dipeptidyl peptidase-4 (DPP-4) inhibitor that raised blood concentrations of GLP-1 and a proton-pump inhibitor (PPI) that raised blood concentrations of gastrin restored normoglycaemia in NOD mice.13 In preparation for translating these results to clinical studies, we showed that these drugs had a similar effect on human islets engrafted into immunodeficient diabetic mice: GLP-1 and gastrin induced β-cell neogenesis from adult human pancreatic exocrine duct cells.14 Therapy with a combination of a DPP-4 inhibitor and PPI stimulated human β-cell neogenesis in these mice.15 A DPP-4 inhibitor in NOD mice reduced insulitis and increased CD4+ CD25+ FoxP3+ cells.16  On the basis of these findings, we postulated that combination therapy with a DPP-4 inhibitor and a PPI would increase GLP-1 and gastrin concentrations in patients. In turn, these increases would act through both direct actions on β cells that promote growth and survival, and modulation of the immunological mechanisms that destroy β cells. We also sought to establish whether combination of a DPP-4 inhibitor and a PPI might improve glucose control, while decreasing insulin use, which are outcomes expected if β-cell function were improved by the intervention.

BODY.METHODS.STUDY DESIGN AND PARTICIPANTS:
REPAIR-T1D is a parallel-group, randomised, double-blind, placebo-controlled, multicentre study. We recruited participants at Sanford Health Systems (Sioux Falls, SD, USA; Fargo, ND, USA), Children's Hospitals and Clinics of Minnesota (St Paul, MN, USA), and Rady Children's Hospital (San Diego, CA, USA).  Participants were eligible if they were aged 11–36 years, diagnosed with type 1 diabetes within the past 6 months (confirmed with at least one positive antibody [GAD or IA-2]), and able to swallow the study capsules. Participants were excluded if they had used a GLP-1 receptor agonist, DPP-4 inhibitor, PPI, or oral hypoglycaemic drug within 1 month before enrolment; had severe hepatic or renal insufficiency; had a history of a serious hypersensitivity reaction to sitagliptin or lansoprazole; had a history of pancreatitis or increased risk of pancreatitis (excessive alcohol intake or history of gallbladder disease); or were women who were pregnant, breastfeeding, or unwilling to delay potential pregnancy for the duration of the study.  The protocol and all consent documents were approved by the appropriate institutional review boards, and written informed consent or assent was obtained. An independent data and safety monitoring board reviewed the study every 3 months.

BODY.METHODS.RANDOMISATION AND MASKING:
Participants were randomly assigned (2:1) to receive the oral DPP-4 inhibitor sitagliptin plus the PPI lansoprazole or matched placebos. Randomisation was done with a blocked randomisation process (blocks of three and six), with separate streams for younger (<18 years) and older (≥18 years) participants, and males and females. Randomisation was done by the study statistician (PAT) after written consent was obtained. All medications were placed into individually numbered vials by the compounding pharmacy at the University of Iowa, IA, USA. Study coordinators were notified by email about which medication vials to use. With the exception of data and safety monitoring board review, all participants and personnel remained masked until after the completion of the final 12 month visit, at which time data were unmasked to the analysis team. The study is ongoing; participants and personnel working directly with participants will remain masked until the final participant completes the study.

BODY.METHODS.PROCEDURES:
Starting at the randomisation visit, participants were given combinations of capsules daily for 12 months. Participants in the treatment group who were 18 years or older received 100 mg sitagliptin and 60 mg lansoprazole, whereas participants younger than 18 years received half of that dose (50 mg sitagliptin and 30 mg lansoprazole). Participants in the placebo group received capsules with identical appearances to the active drugs. Throughout the study, participants continued under the care of their usual provider for routine diabetes management.  Participants returned to clinic at months 3, 6, 9, and 12 after randomisation. Residual β-cell function was assessed at baseline, and 6 and 12 months with a 2-h mixed-meal tolerance test (MMTT). Fasting GLP-1 and gastrin concentrations were measured at these three visits. HbA1c, insulin use, and safety monitoring laboratory values were measured every 3 months. Routine laboratory measurements were done at Sanford Health (Sioux Falls, SD, USA). GLP-1 measurements were done at Pacific Biomarkers (Seattle, WA, USA). Autoantibody concentrations were assayed by immunopreciptiation at Esoterix (Calabasas Hills, CA, USA). HLA typing was done at the University of Minnesota (Minneapolis, MN, USA). C-peptide and gastrin measurements were done at Quest Diagnostics (Chantilly, VA, USA); the C-peptide chemiluminescence assay has a lower limit of detection of 0·03 nmol/L and a coefficient of variation of 2·9–4·8%. Adverse events were classified according to Common Terminology Criteria for Adverse Events (version 4.03). Hypoglycaemic events (blood glucose concentration <3·33 mmol/L) were solicited at every visit by recall and review of meter data. These events were graded as severe if blood glucose concentration was <2·06 mmol/L, or the patient experienced seizure or required medical intervention; the remaining events were grouped together as mild/moderate.

BODY.METHODS.OUTCOMES:
The primary endpoint was predefined as the C-peptide response to a mixed meal challenge at 12 months, measured as the area under the curve (AUC) in 2 h (2-h MMTT). Secondary outcome measures included glucose response to the MMTT (glucose AUC), daily insulin use, and HbA1c. To account for the interrelatedness of HbA1c and insulin use, we calculated insulin dose-adjusted HbA1c (IDA-A1c) as HbA1c (%) + [4 × daily insulin use (units·kg−1d−1)].17 Prespecified and exploratory subgroup analyses are detailed in the appendix.

BODY.METHODS.STATISTICAL ANALYSIS:
Sample size was based initially on clinical and practical considerations. However, a power calculation done at the time of planning the study indicated that, with 54 participants completing the 12-month treatment, we would have a power of 0·9 to detect a 50% protection of C-peptide response. Target enrolment was adjusted to allow for expected attrition.  All data were initially collected on paper forms, and then double entered with the Velos eResearch system (version 9.1.2) with customised data-entry screens. Study monitors (Sanford employees) defined queries for problematic observations. After resolution of queries, data were locked from modification. The primary outcome variable (2-h C-peptide AUC) was analysed with a covariate-adjusted comparison of the log-transformed 12-month values (covariates included age, sex, and base visit value).3,18 Because differences from baseline have a clear interpretation, the interaction between visit and condition (difference of differences) was also examined. Alternative analyses were done (appendix). Although age was used as a stratification variable (<18 years vs ≥18 years) for randomisation, age was treated as a continuous variable for all analyses. All available data were included in all analyses, thus conforming to intention-to-treat principles. Adherence to medication was examined by measurement of expected and actual pill counts with generalised linear models (binomial link) for visit and treatment effects. Tests were done with α=0·05. All analyses were done with SAS (version 9.3) or R (version 3.02).  The adverse events were compared with a generalised linear model with a Poisson link function to examine incidence of adverse events. The two treatments were compared with adverse event category entering as a factor after consolidation of small categories into another group.  This trial is registered with ClinicalTrials.gov, NCT01155284.

BODY.METHODS.ROLE OF THE FUNDING SOURCE:
The study was funded by JDRF Clinical Investigation R & D grant number 17–2010–769 to AR. We thank Denny Sanford for a gift that funded the Sanford Project, and Todd and Linda Broin for funding of Chair for Sanford Project Director (AR). The funders had no role in the study design, implementation, or interpretation, data collections, or writing of the report beyond employment of staff at Sanford Research. AR, KJG, and PAT had access to the complete data and final responsibility for the decision to submit for publication.

BODY.RESULTS:
Between Aug 24, 2010, and May 16, 2012, 265 patients were considered for eligibility (figure 1). This number includes all people who contacted study sites, most of whom were self-referred after news items or finding the study listed on ClinicalTrials.gov. 186 (70%) were either ineligible, declined to participate, or could not be reached after initial contact (figure 1). After initial assessment, 79 participants qualified to give written informed consent and were screened across four sites; 70 were randomly assigned to study groups. After randomisation, two participants withdrew (one was from treatment group and one from placebo group) before taking any drugs, leaving 46 participants in the active treatment group (sitagliptin and lansoprazole) and 22 in the placebo group; 40 participants in the treatment group and 18 in the placebo group completed the 12-month treatment (figure 1). The last patient completed the 12-month treatment on May 23, 2013. Table 1 shows baseline characteristics of patients in the two groups. Pill counts at every visit showed no significant differences in adherence between the two initial groups (sitagliptin: p=0·99; lansoprazole: p=0·87; data not shown).  At 12 months, the 2-h C-peptide AUC did not differ between the two groups after covariate analysis (table 2). Additional adjustments for age, insulin use, and HbA1c with a mixed linear model did not change the results substantially (data not shown). During the course of the study, the C-peptide AUC fell to a similar extent and significantly from baseline in each group (table 2); comparison of these differences was not significant (p=0·91; figure 2A). Blood glucose AUC rose by 2·04 mmol/L (95% CI 1·09–2·99) in the treatment group and 3·05 mmol/L (95% CI 1·17–4·92) in the placebo group, and was not significantly different between groups (p=0·23; figure 2B). HbA1c concentrations were mainly constant throughout the study period for both groups; separate tests were non-significant (p=0·79; figure 2C). Insulin use increased with time in both groups, and was significantly increased for the treatment group over time. The increase was not significant for the placebo group or significantly different between groups (p=0·31; figure 2D). IDA-A1C increased slightly in both groups; the increase was significant for the treatment group with time, but not for the placebo group or between groups (p=0·8; figure 2E). Appendix shows the results of subgroup analyses.  Overall, combination therapy with sitagliptin and lansoprazole was well-tolerated. Table 3 shows a summary of the adverse events, and the appendix provides a detailed listing. No adverse or serious adverse events were probably or definitely related to the study treatment. 87 events were identified as possibly related to treatment, but were distributed equally between treatment and placebo groups (p=0·71). The frequencies of various adverse events and the frequencies of hypoglyacemic events did not differ significantly between the two groups (table 3).

BODY.DISCUSSION:
Our results show that the C-peptide AUC during a 2-h MMTT decreased similarly in both the treatment and placebo groups from baseline to month 12. The mean rates of decline in both groups were similar to that described previously in new-onset type 1 diabetes (panel).25 The trend towards increased insulin use in both groups to maintain similar HbA1c to maintain glycaemic control is also consistent with the expected natural history of type 1 diabetes. The subgroup analyses (appendix) raise the possibility of a differential effect correlating with the extent to which GLP-1 and gastrin were raised by active treatment. The REPAIR-T1D study is ongoing, with reassessments at 18 and 24 months that should help to clarify the size and duration of any benefits from this therapy. With these overall negative results, we are presenting our results in the context of a pilot to inform the design of future studies.  With few participants followed for 1 year, we cannot make a thorough assessment of the safety profile of these drugs in type 1 diabetes. Our data show no difference between groups for gastrointestinal events, which are frequent with incretin-based drugs and can restrict treatment. Although nausea and abdominal pain have also been reported with DPP-4 inhibitors, they tend to be milder than for GLP-1 receptor agonists.26 The numbers of specific events (appendix) are insufficient to establish whether there might be an excess of abdominal pain. The subgroup analyses (appendix) raise the possibility that, in participants who did not increase either GLP-1 or gastrin concentrations, treatment with sitagliptin and lansoprazole might have had a detrimental effect. Although these data are based on a very small subgroup, they are concerning.  As with other intervention studies for type 1 diabetes, the rationale for this trial was based on promising data from rodents and explanted human cells, and an appealing mechanism. Unfortunately, the findings from this study accord with those of many of its predecessors, showing that another approach that reversed diabetes in mice has only a small effect in human beings. Recognition has been growing that traditional animal models of type 1 diabetes are unlikely to provide accurate predictions of clinical success, and that research should shift towards an emphasis on studies in human beings. Human studies, however, are complicated by increased costs, ethics considerations, and substantial variation in genetics and the environment that are not present with laboratory rodents. Recognition is also increasing that type 1 diabetes is not a homogeneous disease. The present challenges—identifying early mechanistic markers that predict success of an intervention and participants who might benefit from different combinations of approaches—are daunting, but urgent.  The inclusion criteria that we used are broader than is typical for similar studies. On the basis of NOD mouse data that showed regeneration of β cells with these drugs after diabetes onset, we chose not to exclude patients with low C-peptide at baseline and to extend eligibility to 6 months after diagnosis. After reviewing the C-peptide responses, we noted that no participants with low C-peptide at entry had recovery. Baseline C-peptide AUC values were not used to stratify randomisation; the active treatment group had a lower baseline value by 0·24 SD (table 1). Although some participants (eight of 29) who had been diagnosed with diabetes for between 3–6 months had C-peptide less than 200 pmol/L, the rest had C-peptide responses that were not distinguishable from those of participants who were enrolled up to 3 months from diagnosis. These data confirm the importance of enrolling only participants who still have sufficient C-peptide production. It is less clear whether the length of time after diagnosis is as important. In this study, those participants entering more than 3 months after diagnosis but who still maintained C-peptide production did not seem to have a worse course than those entering within the first 3 months after diagnosis.  Previous studies have used an entry criterion of peak C-peptide greater than 200 pmol/mL; our data confirm the necessity of a C-peptide response at entry, but are not sufficient to refine this threshold. Although a short duration of disease is often regarded as important to maximise C-peptide at entry, this duration might not be as important by itself. Participants recruited more than 100 days after diagnosis, but who still had C-peptide production, were indistinguishable from those enrolled sooner after diagnosis. Persistent C-peptide production months after diagnosis could reflect a milder underlying disease state and have a lower threshold for a drug to achieve the desired effect. Our results do not show differential effects based on sex. In the present regulatory environment, most drugs will need to be studied in adults. Participants older than 21 years at diagnosis might have a slower rate of C-peptide loss without intervention than those younger than 21 years.21 At a minimum, randomisation must be stratified to ensure even distribution of these adult participants, and interpretation of results should be in the context of this underlying heterogeneity. Detailed, mechanistic examination of the effects on immunophenotype are increasingly crucial in the study of this autoimmune disease and should be included in all future studies. Studies should also include additional samples to be saved to test new hypotheses.  This study has several limitations. In retrospect, this study was underpowered to detect the size of changes given the amount of variability in measurements. The power of the study falls still further when the number of participants is limited to those who had raised GLP-1 and gastrin concentrations, and who had substantial C-peptide production at baseline. This study also did not examine potential immunological effects. Despite these limitations, these results are important pilot data to inform future studies.  Palmer and colleagues3 presented a detailed analysis and discussion of power for similar studies. Based on TrialNet natural history data, they calculated that for a power of 0·85 to detect a 50% difference in C-peptide with an α of 0·05, 172 participants would be required to complete the study; this number is far larger than any type 1 diabetes intervention study so far. Lachin and colleagues18 presented similar discussion based on data from TrialNet intervention studies: with similar assumptions, their calculated sample sizes that are somewhat smaller (as small as 60) at 12 months, but similar to those from Palmer and colleagues3 when including various age strata. Our study is not alone in being underpowered. Other studies have shown non-significant trends in several outcome variables with effect sizes of 25–35%.5,7,27,28 To detect a smaller effect size in this range would require an even larger study. Resources for such trials, including available participants, are insufficient. As biomarkers become available for early assessment of an individual's response to intervention, adaptive trial designs will be more feasible. Until then, we must choose between doing fewer, large, well-powered studies or more smaller studies that are unlikely to give definitive answers, but which might provide preliminary information about several different approaches.  Specific to future studies with drugs acting though GLP-1 and gastrin, we recommend testing participants to ensure that GLP-1 and gastrin concentrations are maintained at concentrations greater than those of untreated individuals (eg, GLP-1 >11 pmol/L and gastrin >16·7 pmol/L) in this study. The slight advantages of using a GLP-1 receptor agonist instead of a DPP-4 inhibitor are shown in the appendix. Drugs that decrease gastric emptying or increase insulin sensitivity might reduce stimulation of β cells and suppress C-peptide production. For these drugs, specification of additional measures of β-cell preservation and function will be important.  Overall, this study did not show an effect of combination therapy with sitagliptin and lansoprazol on C-peptide AUC in patients with new-onset type 1 disease. We noted a slight trend towards preservation of β-cell function in a subgroup who produced increased concentrations of GLP-1 and gastrin while taking the study drug (appendix). Although the size of this effect is slight and necessarily tentative, a future trial might investigate treatment with PPI combined with a GLP-1 receptor agonist in type 1 diabetes. There is growing consensus that the immune attack on β cells is unlikely to be responsive to any approach involving one drug, and that combination therapy is probably necessary.29,30 Because GLP-1 and gastrin are postulated to help β cells to regenerate, they are attractive targets to combine with one or more immunomodulatory drug. A recent review1 concurs with this notion, and also emphasises the extent to which intervention studies for type 1 diabetes have shown heterogeneity in responses, a pattern seen again in our study. To the extent that increased insulin production might stimulate autoimmunity, there is at least a risk that combined DPP-4 inhibitor and PPI therapy might worsen rather than protect against β-cell damage. A possible approach to ameliorate this risk might be to begin therapy with an immunomodulatory drug to decrease the intensity of autoimmunity, followed, after an appropriate interval, with the initiation of combination treatment with GLP-1 receptor agonist and PPI drugs.  For the protocol see http://www.sanfordresearch.org/ClassLibrary/Page/Images/files/SanfordResearch_Trial_PROTOCOL_%202012.pdf

Question: Compared to Placebo what was the result of Sitagliptin and lansoprazole on C-peptide AUC?
Evidence: During the course of the study, the C-peptide AUC fell to a similar extent and significantly from baseline in each group (table 2); comparison of these differences was not significant (p=0·91; figure 2A).
Answer: no significant difference