Dipeptidyl Peptidase IV Inhibition Does Not Adversely Affect Immune ...

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Dipeptidyl Peptidase IV Inhibition Does Not Adversely Affect Immune or Virological Status in HIV Infected Men And Women: A Pilot Safety Study Scott R. Goodwin, Dominic N. Reeds, Michael Royal, Heidi Struthers, Erin Laciny, and Kevin E. Yarasheski Department of Internal Medicine, Washington University School of Medicine, St Louis, Missouri 63110

Context: People infected with HIV have a higher risk for developing insulin resistance, diabetes, and cardiovascular disease than the general population. Dipeptidyl peptidase IV (DPP4) inhibitors are glucose-lowering medications with pleiotropic actions that may particularly benefit people with HIV, but the immune and virological safety of DPP4 inhibition in HIV is unknown. Objective: DPP4 inhibition will not reduce CD4⫹ T lymphocyte number or increase HIV viremia in HIV-positive adults. Design: This was a randomized, placebo-controlled, double-blind safety trial of sitagliptin in HIVpositive adults. Setting: The study was conducted at an academic medical center. Participants: Twenty nondiabetic HIV-positive men and women (9.8 ⫾ 5.5 years of known HIV) taking antiretroviral therapy and with stable immune (625 ⫾ 134 CD4⫹ T cells per microliter) and virological (⬍48 copies HIV RNA per milliliter) status. Intervention: The intervention included sitagliptin (100 mg/d) vs matching placebo for up to 24 weeks. Main Outcome Measures: CD4⫹ T cell number and plasma HIV RNA were measured every 4 weeks; fasting serum regulated upon activation normal T-cell expressed and secreted (RANTES), stromal derived factor (SDF)-1␣, Soluble TNF receptor II, and oral glucose tolerance were measured at baseline, week 8, and the end of study. ANOVA was used for between-group comparisons; P ⬍ .05 was considered significant. Results: Compared with placebo, sitagliptin did not reduce CD4⫹ T cell count, plasma HIV RNA remained less than 48 copies/mL, RANTES and soluble TNF receptor II concentrations did not increase. SDF1␣ concentrations declined (P ⬍ .0002) in the sitagliptin group. The oral glucose tolerance levels improved in the sitagliptin group at week 8. Conclusions: Despite lowering SDF1␣ levels, sitagliptin did not adversely affect immune or virological status, or increase immune activation, but did improve glycemia in healthy, nondiabetic HIV-positive adults. These safety data allow future efficacy studies of sitagliptin in HIV-positive people with cardiometabolic complications. (J Clin Endocrinol Metab 98: 743–751, 2013)

ISSN Print 0021-972X ISSN Online 1945-7197 Printed in U.S.A. Copyright © 2013 by The Endocrine Society doi: 10.1210/jc.2012-3532 Received October 4, 2012. Accepted November 13, 2012. First Published Online December 21, 2012

Abbreviations: AUC, Area under the curve; BMI, body mass index; DAIDS, Division of AIDS; DPP4, dipeptidyl peptidase-IV; GLP-1, glucagon-like peptide-1; HAART, highly active antiretroviral therapies; HDL-c, high-density lipoprotein cholesterol; LDL-c, low-density lipoprotein cholesterol; NRTI, nucleoside reverse transcriptase inhibitor; OGTT, oral glucose tolerance test; PBMC, peripheral blood monocyte cell; RANTES, regulated upon activation normal T cell expressed and secreted; SDF-1␣, stromal derived factor-1␣; sTNFRII, soluble TNF receptor II; T2DM, type 2 diabetes mellitus.

J Clin Endocrinol Metab, February 2013, 98(2):743–751

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Safety of Sitagliptin in HIV

eople with HIV infection are living longer, aided by the development of highly active antiretroviral therapies (HAART). Since the widespread use of these therapies, HIV infection has been transformed into a manageable chronic condition (1). HIV infection and HAART are associated with several cardiometabolic risk factors, including diabetes. The prevalence of insulin resistance and diabetes in HIV-infected adults treated with HAART is as high as 37%, whereas their prevalence is only 2%–15% in the general population (2). The incidence of fasting glucose intolerance or hyperinsulinemia or type 2 diabetes mellitus (T2DM) in HIV-infected people taking HAART is 2– 4 times higher than the general population (3). The pathogenesis of diabetes in HIV is multifactorial and includes traditional risk factors (eg, age, obesity, family history, and physical inactivity), and HIV-specific factors [eg, antiretroviral medications, adipose maldistribution, and proinflammatory processes associated with chronic HIV infection (2– 6)]. HIV-related diabetes is characterized by peripheral and hepatic insulin resistance (7–10), insulin-secretory defects (6, 11), hepatic steatosis (8 –10), central adiposity (12), and increased levels of circulating proinflammatory cytokines (8, 13). Identifying safe and effective treatments for insulin resistance and diabetes in HIV is important because they are cardiovascular disease risk factors that contribute to the 2-fold higher risk for myocardial infarction, stroke and vascular disease in HIV-infected people (14, 15). Dipeptidyl peptidase-IV (DPP4) inhibitors (Januvia; sitagliptin) are a newer class of antidiabetic therapies that lower blood glucose by prolonging the effects of incretin hormones (16 –21). After a meal, the gut releases incretin hormones [glucagon-like peptide-1 (GLP-1) and glucosedependent insulinotropic polypeptide] that increase prandial insulin release (18, 21). GLP-1 stimulates insulin synthesis and secretion and suppresses glucagon secretion, gastric emptying, and appetite (21, 22). Both GLP-1 and glucose-dependent insulinotropic polypeptide promote ␤-cell proliferation and inhibit apoptosis, leading to expansion of ␤-cell mass (18, 21). DPP4 degrades and inactivates incretin hormones, so DPP4 inhibition prolongs the circulating half-life of these incretin hormones and reduces circulating glucose levels after a meal or oral glucose challenge (19, 22). In contrast to several other diabetic medications, DPP4 inhibitors are well tolerated, with a low risk for hypoglycemia, and do not cause weight gain. In T2DM, the DPP4 inhibitor sitagliptin and the GLP-1 agonist exenatide produced rapid and potent antiinflammatory effects in peripheral blood mononuclear cells (16, 23). These antiinflammatory actions might be antiatherogenic, and a recent meta-analysis (⬎41,000 T2DM patients) reported that DPP4 inhibition reduced the risk for

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major cardiovascular events, especially myocardial infarction (24). DPP4 activity has other regulatory functions that may particularly affect HIV-infected people with T2DM (25– 27). DPP4 is identical with CD26, a cell surface glycoprotein chemokine receptor with DPP4 enzyme activity in its extracellular domain. CD26/DPP4 is involved in T cell activation, signal transduction, and interactions between antigen presenting cells and CD4⫹ T cells (27, 28). In vitro, DPP4 cleaves and regulates the functional activity of several immunologically important substrates, including the chemokines regulated upon activation normal T cell expressed and secreted (RANTES; or chemokine ligand 5) and stromal derived factor-1␣ [SDF-1␣; (29, 30)]. It is unknown whether DPP4 inhibition would be detrimental or beneficial to the immune system of people living with HIV. DPP4 inhibitors can block RANTES cleavage, thereby potentially facilitating HIV entry into T lymphocytes (29, 31), and inhibit cleavage of SDF-1␣, potentially blocking HIV entry into T lymphocytes (32, 33). Soluble TNF receptor II (sTNFRII) binds circulating TNF, is a marker for immune cell activation, and has been associated with inflammation and insulin resistance in HIV-infected people (34, 35). We hypothesized that sitagliptin administration would not adversely affect the immune system of HIV-infected adults by lowering CD4⫹ T lymphocyte number, increasing plasma HIV viremia or immune activation.

Materials and Methods HIV-infected adults (18 – 65 years old) were recruited from the AIDS Clinical Trials Unit and the Infectious Diseases Clinic at Washington University School of Medicine. Thirty-one candidates were screened and 20 were enrolled; all participants were HIV positive but were otherwise healthy with stable immunological and virological status on HAART. Stable immunological and virological status was defined as CD4⫹ T cell number greater than 350 cells/␮L and plasma HIV viremia less than 48 copies RNA/mL on the same HAART regimen for the prior 12 months. None of the participants had an AIDS-defining diagnosis, chronic kidney or liver dysfunction, prior pancreatitis, or active malignancy. Participants did not have T2DM or insulin resistance and therefore had fasting glucose values less than 100 mg/dL, fasting insulin levels less than 15 ␮U/mL, a homeostasis model of insulin resistance index less than 3.0, and were not taking any agents that alter blood glucose levels. This study was approved by the Human Research Protection Office at Washington University School of Medicine. All participants provided verbal and written informed consent before participating. The study was registered with ClinicalTrials.gov (NCT01093651). This was a prospective, double-blind, pilot safety study of sitagliptin (100 mg/d) vs matching placebo for up to 24 weeks. At baseline, participants were randomized to a treatment group


(sitagliptin vs placebo) using a block randomization method generated by the pharmacist. The primary outcome was CD4⫹ T cell number and plasma HIV viremia. Secondary outcomes included surrogate markers of immune activation (SDF-1␣, RANTES, and sTNFRII levels), oral glucose tolerance, and safety parameters (kidney function, liver enzymes, complete blood cell counts, fasting lipid/lipoprotein profiles, and adverse symptom assessments). The research pharmacist distributed a 1-month supply of sitagliptin or matching placebo tablets to each participant during each monthly visit. Participants were instructed to take 1 tablet each day with their lunch meal. Anti-HIV medications are typically taken in the morning, so to minimize potential drug interactions, the study drug was taken later in the day. For the first month, participants used a glucometer to document their random and fasting blood glucose concentrations to protect against hypoglycemia. At the baseline visit and every 4 weeks of the study, fasting blood samples were analyzed for CD4⫹ T lymphocytes [absolute number and percentage of peripheral blood monocyte cells (PBMCs)]; plasma HIV viremia (HIV RNA copies per milliliter); and safety laboratory tests including complete metabolic panels, complete blood cell counts, and fasting lipid/lipoprotein profiles. CD4⫹ T cell counts were measured using flow cytometry (Quest Diagnostics, Madison, New Jersey). Plasma HIV viremia was measured using a quantitative PCR assay (COBRAS/Ampli Prep TaqMan HIV-1 test, version 2.0; Roche Molecular Systems Inc, Branchburg, New Jersey) at the Washington University Retrovirology Laboratory or Mayo Medical Laboratories. Other blood chemistries (safety laboratory tests) were analyzed by the Core Laboratory for Clinical Studies at Washington University. An adverse symptom questionnaire was administered every 4 weeks. This questionnaire was based on the Division of AIDS (DAIDS) standardized tool for grading toxicity and severity of adverse events (http://rsc.tech-res.com/default.aspx, August 2009). Serum markers of immune activation (sTNFRII), soluble DPP4 levels, and DPP4 substrates (SDF-1␣/chemokine ligand 12, and RANTES/chemokine ligand 5) were quantified at baseline, week 8, and the end of the study. Samples were batch analyzed using several ELISAs (R&D Systems, Minneapolis, Minnesota). The average of duplicate absorbance (at 570 nm) intensity readings (Tecan microplate reader; Tecan Systems, Inc, San Jose, California) for each standard and sample adjusted to background absorbance (blank) was used to calculate sample concentration using the standard curve approach. All samples for each participant were analyzed in duplicate on the same plate, and the intraassay coefficient of variability for all ELISAs was less than 10%. Fasting 2-hour, 75-g oral glucose tolerance tests with measures of glucose and insulin concentration every 30 minutes were conducted at baseline, week 8, and the end of the study. Plasma glucose concentrations were quantified using a Yellow Springs Instrument (Yellow Springs, Ohio) glucose analyzer. Insulin concentrations were quantified using a chemiluminescent immunometric method (Immulite; Siemens, Los Angeles, California) in the Core Laboratory for Clinical Studies. Once a participant completed the study, their plasma samples from baseline, week 8, and the end of the study were batch analyzed for insulin concentration.


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Statistical analyses Group characteristics and measured variables are reported as mean ⫾ SD. Significance was accepted at P ⱕ .05. Baseline categorical variables were compared using a Fisher’s exact test, and continuous variables were compared using both parametric (when normally distributed) and nonparametric tests (Wilcoxon rank sum test). During the intervention, linear mixed models were used to assess the differences in outcomes [eg, CD4, body mass index (BMI), blood chemistry, chemokines] between the sitagliptin and placebo groups. Study subject was included in these models as a random variable to account for within-participant correlation. Pairwise contrasts were performed to assess the differences in outcome measures between groups at each time point and within a group at each time point. After enrolling the first 7 participants, the study duration was shortened from 24 to 16 weeks for budgetary reasons. For the remaining 13 participants, the laboratory samples scheduled to be drawn at week 24 were instead obtained at week 16. In the initial 7 participants, analytical values from weeks 16 and 24 were averaged to report a single value for the time point referred to as end of study. The original schedule for laboratory assessments at the other time points was not changed. At the completion of the study, it was revealed that of the 7 participants who completed 24 weeks, 4 had received placebo and 3 had received sitagliptin.

Results Baseline characteristics At baseline, the groups were matched for age, gender, and race/ethnicity (Table 1). Virological and immunological parameters, the duration of HIV infection (placebo, 7.6 ⫾ 4.6 vs sitagliptin, 11.2 ⫾ 6.3 yr; P ⫽ .19), and the nadir CD4⫹ T cell counts (self-report) were not different (P ⬎ .05) between groups (placebo, 174 ⫾ 124 vs sitagliptin, 202 ⫾ 140 cells/␮L; P ⫽ .68; Table 1). Baseline CD4⫹ T cell numbers (absolute) were not different between the groups (placebo, 602 ⫾ 91 vs sitagliptin, 648 ⫾ 185 cells/␮L; P ⫽ .48), and CD4⫹ T cell number as a percentage of PBMCs (CD4 percentage) was not different between the groups (placebo, 33.9 ⫾ 5.1 vs sitagliptin, 36.5 ⫾ 6.3%; P ⫽ .33; Table 1). Baseline plasma HIV viremia was below the level of detection (⬍48 copies HIV RNA/mL ⫽ undetectable) in all participants. All participants were receiving HAART for several years (placebo, 6.4 ⫾ 4.4 vs sitagliptin, 8.3 ⫾ 5.1 yr; P ⫽ .43), and the type of HAART was not different between the groups (Table 1). Baseline adiposity (BMI, waist circumference), glycemic control [fasting glucose and insulin, 2 hour oral glucose tolerance test (OGTT) glucose], fasting serum triglycerides, cholesterol and lipoprotein[low-density lipoprotein cholesterol (LDL-c), high-density lipoprotein cholesterol (HDL-c)] concentrations, resting blood pressures (systolic, diastolic), and tobacco use were not different between the groups (all P ⬎ .05; Tables 1 and 2). Two participants in each group were treated for hypertension

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Table 1. Demographics and Baseline Characteristics Parameter Age, y Female gender Race Black White Years since HIV diagnosis Baseline CD4, cells/␮L Baseline CD4, % Nadir CD4, cells/␮L HAART NRTI Zidovudine Lamivudine Abacavir Emtricitabine Tenofovir NNRTI Nevirapine Efavirenz PI Ritonavir Atazanavir Years on HAART BMI, kg/m2 Waist, cm Fasting insulin, ␮U/mL Fasting glucose, mg/dL 2-h OGTT glucose, mg/dL Systolic BP, mm Hg Diastolic BP, mm Hg History HTN Statin use Current tobacco use Years smoked tobacco

Sitagliptin (n ⴝ 10) 36.3 ⫾ 9.2 1 (10%)

Placebo (n ⴝ 10) 40.5 ⫾ 14.9 2 (20%)

7 (70%) 3 (30%) 11.2 ⫾ 6.3 648 ⫾ 185 36.5 ⫾ 6.3 202 ⫾ 140

5 (50%) 5 (50%) 7.6 ⫾ 4.6 602 ⫾ 91 33.9 ⫾ 5.1 174 ⫾ 124

20% 30% 30% 60% 60%

0% 10% 10% 90% 100%

10% 60%

10% 60%

30% 30% 8.3 ⫾ 5.1 26.1 ⫾ 5.6 89 ⫾ 15 6⫾4 90 ⫾ 5 105 ⫾ 28 125 ⫾ 17 77 ⫾ 8 2 (20%) 1 (10%) 4 (40%) 13.8 ⫾ 7.7

20% 30% 6.4 ⫾ 4.4 28.7 ⫾ 4.2 94 ⫾ 6 7⫾5 85 ⫾ 12 110 ⫾ 23 120 ⫾ 14 74 ⫾ 14 2 (20%) 3 (30%) 4 (40%) 11.2 ⫾ 5.7

P Value .46 1.00 .65 .19 .55 .39 .68 1.00

.43 .25 .32 .60 .23 .66 .48 .64 1.00 .58 1.00 .53

Abbreviations: NNRTI, nonnucleoside reverse transcriptase inhibitor; PI, HIV protease inhibitor; BP, blood pressure; HTN, hypertension. Values are means ⫾ SD or n (percentage of participants). P values were derived from independent-sample t tests for measured variables and Fisher’s exact test for categorical variables.

(P ⫽ 1.0). Three placebo participants and 1 sitagliptin participant were receiving a statin medication for hyperlipidemia, but this difference was not statistically significant (P ⫽ .58).

Immune and virological parameters During sitagliptin exposure, CD4⫹ T cell counts (absolute and percentage) were unchanged from baseline values, did not differ between the 2 groups, and no participant experienced a

Table 2. Serum Triglycerides, Cholesterol, and Lipoprotein Concentrations (Milligrams per Deciliter) at Baseline and during Sitagliptin vs Placebo Exposure Week Parameter Triglycerides Total cholesterol LDL-c HDL-c

Group Placebo Sitagliptin Placebo Sitagliptin Placebo Sitagliptin Placebo Sitagliptin

0 112 ⫾ 74 85 ⫾ 27 168 ⫾ 31 194 ⫾ 39 101 ⫾ 32 122 ⫾ 36 46 ⫾ 15 56 ⫾ 12

4 118 ⫾ 105 113 ⫾ 53 170 ⫾ 31 190 ⫾ 45 97 ⫾ 31 116 ⫾ 34 50 ⫾ 17 53 ⫾ 16

8 120 ⫾ 72 88 ⫾ 39 161 ⫾ 22 181 ⫾ 42 91 ⫾ 25 111 ⫾ 34 46 ⫾ 15 53 ⫾ 14

Mean ⫾ SD. No between-group differences were detected at any time point. a

P ⫽ .004 vs week 0 in sitagliptin group.

12 118 ⫾ 53 90 ⫾ 25 180 ⫾ 29 185 ⫾ 48 107 ⫾ 25 104 ⫾ 32a 49 ⫾ 16 57 ⫾ 19

16 113 ⫾ 69 103 ⫾ 62 173 ⫾ 27 178 ⫾ 34 101 ⫾ 25 104 ⫾ 25a 48 ⫾ 15 53 ⫾ 14

P Value Group ⴛ Time .28 .17 .01 .34


A

900 800 700

mL) SDF-1α(pg/m

2500

Placebo Sitagliptin

*

1000

400

100

*

Placebo Sitagliptin

500 0 120

B RANTES (ng/mL)

CD4+ T-lym mphocytes (% PB MCs)

A

1500

500

45

747

2000

600

B

40 35

80 60 40 20

0 3500

30 25 20 0

4

8

12

16

20

24

Time (weeks) Figure 1. Immunological and virological status. CD4⫹ T lymphocyte number (A) absolute count, and (B) percentage of PBMCs were not different between the groups at baseline (P ⫽ .55 and P ⫽ .39, respectively) and not different at any time point during sitagliptin or placebo exposure (P ⫽ .58 and P ⫽ .82, respectively). Additionally, plasma HIV RNA copy number remained undetectable (⬍48 copies HIV RNA/mL) at all time points in both groups throughout the study period. The data points at week 24 represent n ⫽ 4 placebo and n ⫽ 3 sitagliptin.

clinically significant decline in CD4⫹ T cell number (Figure 1, A and B), defined as a value less than 250 cells/␮L or a 30% decline from their baseline CD4⫹ T cell count. At baseline, plasma HIV viremia was less than 48 copies HIV RNA/mL (undetectable) in all participants and remained undetectable in all participants at all time points during placebo or sitagliptin exposure. Chemokines and markers of immune activation Baseline serum SDF-1␣ concentrations were not different between the sitagliptin (2378 ⫾ 441 pg/mL) and placebo (2327 ⫾ 304 pg/mL) groups (Figure 2A). SDF-1␣ concentrations were not altered during the study in the placebo group. In contrast, total SDF-1␣ concentrations (intact ⫹ cleaved) declined approximately 50% in the sitagliptin group at week 8 (1208 ⫾ 605 pg/mL, P ⬍ .0001), and this decline persisted until the end of the study (1277 ⫾ 490 pg/mL, P ⬍ .0001). There were no betweenor within-group differences for serum RANTES or sTNFRII concentrations (Figure 2, B and C).

Solube TN NF receptor-II (pg g/mL)

CD D4+ T-lymph ocytes (cells/µL )

1000


3000

C

2500 2000 1500 1000 500 0

Baseline

Week 8 Time (weeks)

Week 16-24

Figure 2. Chemokines and markers of immune activation. A, Baseline serum SDF-1␣ concentrations were not different between the groups (P ⫽ .80), but at week 8 and the end of study, SDF-1␣ levels were lower in the sitagliptin group than in the placebo group. *, P ⬍ .0001. B, Serum RANTES levels were not different between the groups at baseline (P ⫽ .27) and were not different at any time point during placebo or sitagliptin exposure (P ⬎ .25). C, Serum sTNFRII levels were not different between the groups at baseline (P ⫽ .60) and were not different at any time point during placebo or sitagliptin exposure (P ⬎ .28).

Baseline serum soluble DPP4 concentrations were similar between the groups (placebo, 452 ⫾ 115 vs sitagliptin, 460 ⫾ 130 ng/mL). At the end of study, there was a trend toward higher DPP4 concentrations in the sitagliptin (484 ⫾ 158 ng/mL) vs the placebo group (424 ⫾ 110 ng/mL), but this difference was not statistically significant (P ⫽ .17, group ⫻ time interaction). Fasting triglycerides, cholesterol, and lipoproteins Baseline fasting concentrations of total cholesterol, LDL-c, HDL-c, and triglycerides were not different between the sitagliptin and placebo groups (Table 2). Overall, there were no between-group differences in these parameters at any time point during the study. Within the sitagliptin group, the group ⫻ time interaction (P ⫽ .01)

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A. Baseline

150

120

120

90

90 60

Placebo Sitagliptin Placebo AUC Sitagliptin AUC

30

0 180 B. Week 8

30 0 180

*

*

150

150

120 90

120

*

90

60

60

30

30

0 180

0 180

C End Study C.

150 120 90

different between the groups [OGTT glucose AUC for placebo ⫽ 14 247 ⫾ 2662 mg/dL 䡠 min, sitagliptin ⫽ 14 564 ⫾ 3246 mg/dL 䡠 min (P ⫽ .81; Figure 3); OGTT insulin AUC for placebo ⫽ 5775 ⫾ 3607 ␮U/mL 䡠 min, sitagliptin ⫽ 6397 ⫾ 3396 ␮U/mL 䡠 min (P ⫽ .70)]. At week 8, the OGTT glucose AUC was lower (P ⫽ .03) in the sitagliptin group (⫺1201 ⫾ 2669 mg/dL 䡠 min) than in the placebo group (⫹1555 ⫾ 2499 mg/dL 䡠 min), primarily due to lower time 0 (fasting) and 60-minute glucose values (P ⬍ .04). At the end of study, OGTT glucose AUC was not different from baseline in either group (P ⬎ .08) and no longer differed between the groups (P ⫽ .12; placebo ⫽ 15 752 ⫾ 2317 and sitagliptin ⫽ 14 249 ⫾ 2154 mg/ dL 䡠 min). At week 8 and the end of the study, OGTT insulin AUC was not different from baseline in either group (P ⬎ .08) and was not different between the groups (P ⬎ .27).

180

150

60

e (mg/dL)) Glucose


AUC C (x100)

748

150 120

*

90

60

60

30

30

0

0 0

30

60

90

120

150

Time (min) Figure 3. Oral glucose tolerance. A, Baseline glucose values and area under the OGTT curve were not different between the groups (P ⬎ .50). B, After 8 weeks of sitagliptin exposure, fasting glucose, glucose at 60 min, and AUC were lower for sitagliptin than placebo. *, P ⬍ .04. C, At the end of the study, only fasting glucose levels remained lower in sitagliptin than placebo. *, P ⫽ .0004.

detected a decrease in LDL-c at week 12 and the end of study in comparison with week 0, but this was not different from the LDL-c fluctuations observed in the placebo group (Table 2). Renal function, serum electrolytes, hepatic function, and complete blood cell counts remained stable in all participants during the study and no between group differences were observed. Two-hour OGTT parameters Baseline glucose and insulin values during the OGTT were normal and the area under the curves (AUCs) was not

Drug tolerability and toxicity All 20 participants completed the study. At each visit, the study pharmacist or his designee assessed participant adherence to drug using recall and pill counts. Overall compliance in the sitagliptin group was 96.6% (94%– 100% minimum-maximum compliance). At every visit, each participant completed an adverse symptom questionnaire. A study physician (blinded to group assignment) evaluated all reported adverse symptoms and quantified the severity using the standardized DAIDS risk assessment tool. There were 3 reports of hypoglycemic symptoms in the sitagliptin group vs 1 report in the placebo group (P ⫽ .35; Table 3). The lowest documented blood glucose (glucometer) during the study was 70 mg/dL; this occurred in a sitagliptin recipient after a prolonged overnight fast (⬃16 hours). There were no adverse symptoms graded greater than 2 (moderate) on the DAIDS scale in the sitagliptin group.

Discussion Immune and virological safety of DPP4 inhibition was evaluated so that future efficacy studies can be conducted in people living with HIV, a population with an approximately 2-fold greater risk for diabetes and cardiovascular

Table 3. Cumulative Frequency of Self-Reported Symptoms

Sitagliptin Placebo

Hypoglycemic Symptoms (Faint, Lightheaded, Anxiety That Is Relieved with Food)

GI Symptoms (Abdominal Pain, Nausea, Diarrhea)

URI Symptoms (Nasal Congestion, Cough, Sore Throat)

Generalized Fatigue

Headache

Other (Rash, Musculoskeletal Pain, Mood Changes)

3 1

3 8

5 10

2 5

4 5

5 6

Abbreviations: GI, gastrointestinal; URI, upper respiratory infection. Values reflect cumulative number of self-reported specific symptoms during entire study. Hypoglycemic symptoms were reported in both groups. Numerically, all other symptoms were reported more frequently in the placebo group. There were no symptoms rated greater than 2 (moderate) on the DAIDS severity scale in the sitagliptin group.


disease than the general population. The findings from this randomized, placebo controlled safety trial suggest that 4 – 6 months of sitagliptin exposure (100 mg/d) did not reduce CD4⫹ T cell number (absolute or percentage PBMCs) or increase plasma HIV RNA copy number (viremia) in nondiabetic HIV-positive men and women. In addition, sitagliptin exposure did not increase sTNFRII concentrations, a marker of immune activation. Sitagliptin exposure did not adversely alter fasting serum lipids/ lipoprotein concentrations or any other standard clinical chemistry laboratory value. These findings suggest that sitagliptin can be safely administered and is well tolerated by HIV-infected adults with stable immunological and virological status who are taking contemporary nonnucleoside reverse transcriptase inhibitor (NRTI)- and HIV protease inhibitor-based antiretroviral drug therapies. Efficacy trials of this agent should be pursued in insulinresistant and glucose-intolerant HIV-infected adults because their cardiometabolic phenotype (peripheral and central insulin resistance, insulin secretory defects, hepatosteatosis, endothelial dysfunction, diabetic cardiomyopathy, inflammation, and atherosclerosis) may be particularly responsive to the reported beneficial actions of DPP4 inhibition and incretin therapy (16 –18, 21, 23, 24). Minor safety concerns included reports of hypoglycemia symptoms and the decline in serum SDF-1␣ concentration in the sitagliptin group. Hypoglycemia symptoms were reported in both groups, but there were no documented blood glucose concentrations less than 65 mg/dL. Oral glucose tolerance was only modestly improved at week 8, most likely due to the limited potential to further improve oral glucose tolerance in people with normal glucose tolerance at baseline. Intact (uncleaved) SDF-1␣ is a chemokine ligand for the T-cell CXCR4 (C-X-C chemokine receptor type 4) and is capable of blocking HIV entry, so a reduction in serum SDF-1␣ concentration might be predicted to facilitate HIV entry and potentially lower CD4⫹ T cell number and increase plasma HIV viremia. These adverse immune and virological outcomes were not observed, and a marker of immune activation (sTNFRII) was unchanged during sitagliptin exposure. Using a different assay for immune activation, White et al (36) reported no effect of sitagliptin (100 mg/d for 6 months) on CD4⫹ T cell activation in an observational study of T2DM (not HIV positive). It is possible that long-term sitagliptin exposure is required before adverse immune and virological outcomes are noted. Alternatively, even with lowered (⬃50%) SDF-1␣ concentrations, an adequate amount of SDF-1␣ may have remained to protect T cells from HIV entry. CD26/DPP4 is ubiquitously expressed and can therefore contribute to alterations in serum SDF-1␣ concentration that do not accurately reflect


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SDF-1␣ concentration at the level of the T cell in which chemokine exposure may be different and under the influence of other regulators. In vitro, intact SDF-1␣ blocks entry of X4 tropic synticium-inducing cytopathic strains of HIV into lymphocytes (32, 33). Our HIV-infected participants with undetectable (suppressed) plasma viremia and relatively short duration of HIV infection may have possessed predominantly R5 tropic virus. R5 tropic virus predominantly exploits the CCR5 (C-C chemokine receptor type 5; not CXCR4) for HIV transmission and replication in vivo. The DPP4-cleaved products of the chemokine RANTES interact with and block the C-C chemokine receptor type 5 from the HIV-1 envelope glycoprotein 120 thereby inhibiting HIV infectivity (37). RANTES concentrations did not change during this study, which is 1 possible explanation for not observing worsening immunologic status. A rapid decline in T cell count and the progression to AIDS are often associated with a switch from R5 to X4 tropic HIV-1 variants (37, 38). The possibility also exists that the ELISA antibody was directed against an epitope that was not specific for full-length intact SDF-1␣, and instead our SDF-1␣ values reflect quantitation of both intact and DPP4-cleaved forms of SDF-1␣. Despite lowering total SDF-1␣ levels, sitagliptin did not adversely affect immune or virological status or increase a marker of immune activation in nondiabetic HIV-positive men and women. The findings from this short duration pilot study indicate that sitagliptin was safe and well tolerated by HIV-infected men and women with stable immunological and virological status receiving contemporary antiretroviral therapies. There could be concern that a type 2 error occurred, given the small sample size. However, the study was powered to detect a clinically significant decline in CD4⫹ T cell count (⬍250 cells/␮L or a 30% decline from baseline CD4⫹ T cell count), the primary outcome. Also, the finding that plasma HIV viremia was less than 48 copies/mL in all participants at all time points during the study supports the claim that this drug was virologically safe. The findings that serum soluble CD26/DPP4 and sTNFRII levels were unchanged during sitagliptin exposure are reassuring, but measures of CD26⫹ T lymphocyte number and more specific markers of immune activation should be obtained in people living with HIV. In T2DM, sitagliptin reduced mononuclear cell CD26 transcript expression (16), a marker for the antiinflammatory actions of sitagliptin. This was coincident with reduced circulating DPP4 enzyme activity and increased circulating DPP4 protein concentrations, suggesting that sitagliptin might release CD26/DPP4 receptors from cell membranes and increase the quantity of DPP4 protein measured in the circulation (16). In the current study, we

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noted a trend toward higher serum soluble DPP4 protein concentrations in the sitagliptin group, but the small sample size prevented this comparison from attaining statistical significance. Given that DPP4 cleaves a large number of substrates with diverse biological, immunological, and endocrinological effects, the long-term safety of DPP4 inhibitors in people with HIV merits careful consideration and analysis. Additionally, these safety data allow future efficacy studies focused on glycemic and pleiotropic actions of sitagliptin in HIV-infected people with insulin resistance, glucose intolerance, and cardiometabolic complications.


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Acknowledgments We thank the participants for their commitment to research studies. Debra Demarco-Shaw, RN, BSN, ACRN, and Lisa Kessels, RN, at The Washington University AIDS Clinical Trials Unit provided assistance with recruitment and testing. Merck Pharmaceuticals provided the sitagliptin and matching placebo tablets. The study was registered as National Institutes of Health Clinical Trial no. 01093651. Address all correspondence and requests for reprints to: Kevin E. Yarasheski, PhD, Professor of Medicine, Cell Biology and Physiology, and Physical Therapy, Washington University School of Medicine, Division of Endocrinology, Metabolism, and Lipid Research, 660 South Euclid Ave, Box 8127, Saint Louis, Missouri 63110. E-mail: [email protected]. This work was supported by the Campbell Foundation, and National Institutes of Health (NIH) grants to the Washington University AIDS Clinical Trials Unit (grant AI069495), Diabetes Research Center (grant DK020579), Institute of Clinical and Translational Sciences (grant RR024992), and Biomedical Mass Spectrometry Research Facility (grants GM103422 and DK056341). S.R.G. was supported by NIH grant T32 DK007120. Disclosure Summary: The authors have nothing to disclose.

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