Efficacy of downtitration or treatment withdrawal compared with continuous dosing after successful treatment with baricitinib in patients with moderate-to-severe atopic dermatitis in a randomized substudy from the long-term extension study BREEZE-AD3.

BACKGROUND: Baricitinib, an oral, selective Janus kinase 1/2 inhibitor, demonstrated long-term efficacy in moderate-to-severe atopic dermatitis in an ongoing double-blind, phase III, long-term extension study, BREEZE-AD3 (NCT03334435). OBJECTIVES: To evaluate the efficacy and safety of downtitration and treatment withdrawal in a substudy of BREEZE-AD3. METHODS: The substudy included patients (N = 526) treated with baricitinib 4 mg or 2 mg at entry into BREEZE-AD3 who achieved a validated Investigator Global Assessment for Atopic Dermatitis (vIGA-AD®) scale score of 0 (clear), 1 (almost clear) or 2 (mild) at week 52. Patients treated with baricitinib 4 mg were rerandomized to baricitinib 4 mg (continuous dosing), baricitinib 2 mg (downtitration) or placebo (treatment withdrawal, 4-mg cohort), and patients treated with baricitinib 2 mg were rerandomized to baricitinib 2 mg (continuous dosing), baricitinib 1 mg (downtitration), or placebo (treatment withdrawal, 2-mg cohort). After 16 weeks, we assessed the proportion of patients with vIGA-AD® 0/1, vIGA-AD® 0/1/2, vIGA-AD® ≥ 3 (loss of response; criterion to readminister the original baricitinib dose) and for patients who were readministered the original baricitinib dose, we assessed the proportion of patients who recaptured vIGA-AD® 0/1/2 within 16 weeks of treatment readministration (patients in the continuous dosing maintained the same dose). RESULTS: For the continuous dosing, downtitration, and treatment withdrawal groups 51%, 45% and 30% of patients in the 4-mg cohort achieved vIGA-AD® 0/1 and 87%, 61% and 50% of patients achieved vIGA-AD® 0/1/2, respectively. For the 2-mg cohort, the respective proportions of patients were 48%, 42% and 25% for vIGA-AD® 0/1 and 92%, 71% and 45% for vIGA-AD® 0/1/2. The respective proportions of patients with vIGA-AD® ≥ 3 were 39%, 49% and 56% in the 4-mg cohort and 41%, 41% and 64% in the 2-mg cohort. Of those who were readministered the original baricitinib dose, the proportions of patients who recaptured vIGA-AD® 0/1/2 among the continuous dosing, downtitration, and treatment withdrawal groups were 80%, 85% and 88% in the 4-mg cohort and 90%, 56% and 86% in the 2-mg cohort, respectively. CONCLUSIONS: Baricitinib allows flexibility for patients to downtitrate or stop treatment. For patients who downtitrated treatment, the majority maintained efficacy through 16 weeks. Most patients who lost efficacy with downtitration or treatment withdrawal achieved clinically relevant efficacy upon readministration of their original dose.

Long-term efficacy (up to 68 weeks) of Baricitinib in combination with topical corticosteroids in adult patients with moderate-to-severe atopic dermatitis: Analysis of treatment responders, partial responders and nonresponders originating from study BREEZE-AD7.

BACKGROUND: Baricitinib demonstrated efficacy in treating adults with moderate-to-severe atopic dermatitis (AD) in Phase 3 clinical trials. OBJECTIVE: To examine long-term efficacy of baricitinib combined with topical corticosteroids (TCS) in adult patients from a Phase 3 study, BREEZE-AD7 (NCT03733301), enrolled in ongoing extension study, BREEZE-AD3 (NCT03334435). METHODS: Upon BREEZE-AD7 completion, responders or partial responders (RPR [vIGA-AD™ ≤2]) receiving baricitinib 2-mg or 4-mg + TCS maintained their original treatment doses in BREEZE-AD3. Nonresponders (NR; vIGA-AD 3,4) receiving baricitinib 2-mg were rerandomized 1:1 to baricitinib 2-mg or 4-mg; NR receiving baricitinib 4-mg remained on same dose. Integrated data from all patients (RPR + NR = baricitinib 4-mg intent-to-treat [ITT] cohort) receiving continuous baricitinib 4-mg in BREEZE-AD7 through BREEZE-AD3 were analysed, along with baricitinib 4-mg or 2-mg RPR cohorts. Primary endpoint was proportion of patients with vIGA-AD (0,1) at Weeks 16, 36 and 52 (Weeks 32, 52 and 68 of continuous therapy). Additional outcomes included improvement in EASI75 and Itch NRS (up to Week 32). Missing data were imputed by last observation carried forward. RESULTS: In baricitinib 4-mg ITT cohort (N = 102), proportions of patients achieving vIGA-AD (0,1) at Week 32, Week 52, and Week 68 were 21.6%, 26.5% and 23.5%; EASI75 were 46.1%, 40.2% and 43.1%, respectively. Itch NRS ≥4-point improvement (Itch ≥4) were 47.3% at Week 16 and 40.6% at Week 32. In baricitinib 4-mg RPR cohort (N = 63), proportions of patients achieving vIGA-AD (0,1) at Week 32, Week 52 and Week 68 were 31.7%, 33.3% 34.9%, respectively; EASI75 were 57.1%, 49.2% and 49.2%, respectively. Itch ≥4 were 53.6% at Week 16 and 46.4% at Week 32. Corresponding proportions for baricitinib 2-mg RPR cohort (N = 53) for vIGA-AD (0,1) were 39.6%, 45.3% and 30.2%; EASI75 were 77.4%, 69.8% and 58.5%, respectively. Itch ≥4 were 56.3% at Week 16 and 47.9% at Week 32. CONCLUSION: Baricitinib 4-mg and 2-mg combined with TCS maintained clinically meaningful sustained efficacy over 68 weeks of continuous treatment.

Baricitinib in Patients with Refractory Rheumatoid Arthritis.

BACKGROUND: In phase 2 studies, baricitinib, an oral Janus kinase 1 and 2 inhibitor, reduced disease activity in patients with rheumatoid arthritis who had not previously received treatment with biologic disease-modifying antirheumatic drugs (DMARDs). METHODS: In this phase 3 study involving 527 patients with an inadequate response to or unacceptable side effects associated with one or more tumor necrosis factor inhibitors, other biologic DMARDs, or both, we randomly assigned the patients in a 1:1:1 ratio to baricitinib at a dose of 2 or 4 mg daily or placebo for 24 weeks. End points, tested hierarchically at week 12 to control type 1 error, were the American College of Rheumatology 20% (ACR20) response (primary end point), the Health Assessment Questionnaire-Disability Index (HAQ-DI) score, the 28-joint Disease Activity Score based on C-reactive protein level (DAS28-CRP), and a Simplified Disease Activity Index (SDAI) score of 3.3 or less (on a scale of 0.1 to 86.0, with a score of 3.3 or less indicating remission). Comparisons with placebo were made first with the 4-mg dose of baricitinib and then with the 2-mg dose. RESULTS: Significantly more patients receiving baricitinib at the 4-mg dose than those receiving placebo had an ACR20 response at week 12 (55% vs. 27%, P<0.001). Differences between the higher-dose baricitinib group and the placebo group were also significant for the HAQ-DI score and the DAS28-CRP but not for an SDAI score of 3.3 or less. Adverse-event rates through 24 weeks were higher for patients receiving the 2-mg dose of baricitinib and those receiving the 4-mg dose than for patients receiving placebo (71% and 77%, respectively, vs. 64%), including infections (44% and 40%, vs. 31%). The rates of serious adverse events were 4%, 10%, and 7% in the three groups, respectively. Two nonmelanoma skin cancers and two major adverse cardiovascular events, including a fatal stroke, occurred in the higher-dose group. Baricitinib was associated with a small reduction in neutrophil levels and increases in serum creatinine and low-density lipoprotein cholesterol levels. CONCLUSIONS: In patients with rheumatoid arthritis and an inadequate response to biologic DMARDs, baricitinib at a daily dose of 4 mg was associated with clinical improvement at 12 weeks. (Funded by Eli Lilly and Incyte; ClinicalTrials.gov number, NCT01721044.).

JAK1/JAK2 inhibition by baricitinib in diabetic kidney disease: results from a Phase 2 randomized controlled clinical trial.

Background: Inflammation signaled by Janus kinases (JAKs) promotes progression of diabetic kidney disease (DKD). Baricitinib is an oral, reversible, selective inhibitor of JAK1 and JAK2. This study tested the efficacy of baricitinib versus placebo on albuminuria in adults with Type 2 diabetes at high risk for progressive DKD. Methods: In this Phase 2, double-blind, dose-ranging study, participants were randomized 1:1:1:1:1 to receive placebo or baricitinib (0.75 mg daily; 0.75 mg twice daily; 1.5 mg daily; or 4 mg daily), for 24 weeks followed by 4-8 weeks of washout. Results: Participants (N = 129) were 63±9.1 (mean±standard deviation) years of age, 27.1% (35/129) women and 11.6% (15/129) African-American race. Baseline hemoglobin A1c (HbA1c) was 7.3±1% and estimated glomerular filtration rate was 45.0±12.1 mL/min/1.73 m2 with first morning urine albumin-creatinine ratio (UACR) of 820 (407-1632) (median; interquartile range) mg/g. Baricitinib, 4 mg daily, decreased morning UACR by 41% at Week 24 compared with placebo (ratio to baseline 0.59, 95% confidence interval 0.38-0.93, P = 0.022). UACR was decreased at Weeks 12 and 24 and after 4-8 weeks of washout. Baricitinib 4 mg decreased inflammatory biomarkers over 24 weeks (urine C-X-C motif chemokine 10 and urine C-C motif ligand 2, plasma soluble tumor necrosis factor receptors 1 and 2, intercellular adhesion molecule 1 and serum amyloid A). The only adverse event rate that differed between groups was anemia at 32.0% (8/25) for baricitinib 4 mg daily versus 3.7% (1/27) for placebo. Conclusions: Baricitinib decreased albuminuria in participants with Type 2 diabetes and DKD. Further research is required to determine if baricitinib reduces DKD progression.

Safety of baricitinib for the treatment of atopic dermatitis over a median of 1.6 years and up to 3.9 years of treatment: an updated integrated analysis of eight clinical trials.

BACKGROUND: Baricitinib, a selective Janus kinase (JAK)1/JAK2 inhibitor, is approved for treatment of moderate-to-severe atopic dermatitis (AD) in adults. OBJECTIVES: We report integrated baricitinib safety data in patients with up to 3.9-years exposure. METHODS: Three datasets from the integrated AD clinical trial program were analyzed: placebo-controlled, 2-mg-4-mg extended, and All-bari. Data cutoffs were up to 21-December-2021 for long-term extension studies. Proportions of patients with events and incidence rates (IR)/100 patient years (PY) at risk were calculated. RESULTS: 2636 patients received baricitinib for 4628.4 PY. Discontinuation due to adverse events was low (IR = 3.4). IRs in All-bari were: serious adverse events, 5.2; infection, 67.2 (any infection), 6.7 (herpes simplex), 2.8 (herpes zoster), and 0.3 (opportunistic infections). Adverse events of special interest in All-bari included seven patients with positively adjudicated major adverse cardiovascular events (MACE) (IR = 0.15), three pulmonary emboli (PE) (IR = 0.06), 14 malignancies excluding nonmelanoma skin cancer (IR = 0.3), one gastrointestinal perforation (IR = 0.02), and four deaths (IR = 0.1). No deep vein thromboses (DVT) or tuberculosis were reported. CONCLUSION: In this analysis, baricitinib maintained a similar safety profile to earlier analyses with no new safety signals. Rates of MACE, DVT/PE, malignancies, and serious infections were within ranges of background rates in patients with AD. CLINICALTRIALS.GOV: NCT02576938 (JAHG), NCT03334396 (JAHL; BREEZE-AD1), NCT03334422 (JAHM; BREEZE-AD2), NCT03334435 (JAHN; BREEZE-AD3), NCT03428100 (JAIN; BREEZE-AD4), NCT03435081 (JAIW; BREEZE-AD5), NCT03559270 (JAIX; BREEZE-AD6), NCT03733301 (JAIY; BREEZE-AD7).

Extended Safety Analysis of Baricitinib 2 mg in Adult Patients with Atopic Dermatitis: An Integrated Analysis from Eight Randomized Clinical Trials.

BACKGROUND: Baricitinib, a selective Janus kinase 1/Janus kinase 2 inhibitor, is indicated in the European Union and Japan for the treatment of moderate-to-severe atopic dermatitis (AD) in adults who are candidates for systemic therapy. OBJECTIVE: The objective of this study was to evaluate the safety of baricitinib 2 mg in the AD clinical program. METHODS: Six double-blind, randomized, placebo-controlled studies, and two long-term extension studies were summarized in two datasets. Placebo comparison was based on six 16-week studies with baricitinib 2 mg. All-bari-2-mg-AD included patients who received baricitinib 2 mg at any time during the eight studies. RESULTS: In total, 1598 patients received once-daily baricitinib 2 mg for 1434.2 patient-years of exposure (median 330 days/maximum 2.4 years). Treatment-emergent adverse events were higher for baricitinib 2 mg (57.9%) vs placebo (51.6%). Serious adverse events, serious infections, and opportunistic infections were low in frequency and similar between baricitinib 2 mg and placebo. There were no malignancies, gastrointestinal perforations, or major adverse cardiovascular events with baricitinib 2 mg in the placebo-controlled period. Herpes simplex (cluster) was higher for baricitinib 2 mg (3.8%) vs placebo (2.8%); rates decreased with extended 2 mg exposure. In All-bari-2-mg-AD, there were five malignancies other than non-melanoma skin cancer, two major adverse cardiovascular events, one peripheral venous thrombosis, one arterial thrombosis, and no pulmonary embolisms, deep vein thromboses, or deaths. CONCLUSIONS: This integrated analysis in patients with moderate-to-severe AD confirms the established safety profile of baricitinib 2 mg. Longer exposure to treatment is required to evaluate risks of malignancies and major adverse cardiovascular events. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov identifiers: NCT02576938 (first posted 15 October, 2015); NCT03334396 (7 November, 2017); NCT03334422 (7 November, 2017); NCT03428100 (9 February, 2018); NCT03435081 (15 February, 2018); NCT03733301 (7 November, 2018); NCT03334435 (7 November, 2017); NCT03559270 (18 June, 2018).

Baricitinib is a medication that helps an overactive immune system adjust itself, leading to improvements in the inflammatory condition atopic dermatitis. Baricitinib is approved for patients with moderate-to-severe atopic dermatitis in 40 countries. Because it works with the immune system, it is important to understand the safety of baricitinib. Safety information was collected from eight studies and analyzed in two datasets. The first dataset compared the safety of baricitinib 2 mg with placebo in six 16-week studies in which neither patient nor physician knew whether they were taking baricitinib or placebo. The second dataset included an additional two extension studies and examined the safety of baricitinib in all patients receiving at least one dose of baricitinib 2 mg. Patients took baricitinib 2 mg for a maximum of 2.4 years, with a median time of 330 days. In the first dataset, adverse events were higher for baricitinib 2 mg (57.9%) than placebo (51.6%). Serious adverse events, serious infections, and opportunistic infections were low in number and similar for patients taking baricitinib 2 mg or placebo. Herpes simplex infections were more frequent in patients taking baricitinib 2 mg (3.8%) than in those taking placebo (2.8%), but rates in those taking baricitinib 2 mg decreased with a longer treatment duration. There were no occurrences of cancer, gastrointestinal perforations, or major adverse cardiovascular events. In the second dataset, there were five reports of cancer other than non-melanoma skin cancer, two major adverse cardiovascular events, one peripheral venous thrombosis, one arterial thrombosis, and no pulmonary embolisms, deep vein thromboses, or deaths. Longer treatment with baricitinib is required to better understand the risks of developing cancer or major adverse cardiovascular events. This analysis of safety in patients with moderate-to-severe atopic dermatitis is consistent with the safety reported previously for baricitinib 2 mg. Extended Safety Analysis of Baricitinib 2 mg in Adult Patients with Atopic Dermatitis: An Integrated Analysis from Eight Randomized Clinical Trials (MP4 87244 kb).

Long-term Efficacy of Baricitinib in Adults With Moderate to Severe Atopic Dermatitis Who Were Treatment Responders or Partial Responders: An Extension Study of 2 Randomized Clinical Trials.

IMPORTANCE: Baricitinib, an oral selective Janus kinase inhibitor, improved the clinical signs and symptoms of moderate to severe atopic dermatitis in the 16-week, phase 3 monotherapy studies, BREEZE-AD1 and BREEZE-AD2. Long-term efficacy has not yet been examined. OBJECTIVE: To evaluate the long-term (68-week) efficacy of baricitinib in adults with moderate to severe atopic dermatitis who were treatment responders or partial responders in BREEZE-AD1 and BREEZE-AD2. DESIGN, SETTING, AND PARTICIPANTS: Patients completing BREEZE-AD1/BREEZE-AD2 entered the ongoing, multicenter, double-blind, long-term extension study BREEZE-AD3. The study was initiated on March 28, 2018. Data were analyzed on December 13, 2019. INTERVENTIONS: Responders and partial responders (patients achieving validated Investigator Global Assessment for Atopic Dermatitis [vIGA-AD] score of 0 or 1 [0,1], or 2) at BREEZE-AD1/BREEZE-AD2 completion remained on originally assigned treatment for 52 weeks (68 total weeks of continuous therapy). MAIN OUTCOMES AND MEASURES: The primary end point was the proportion of patients achieving a vIGA-AD score of 0,1 at weeks 16, 36, and 52 of BREEZE-AD3. Secondary end points included the proportion of patients achieving 75% or more improvement in the Eczema Area and Severity Index [EASI75] score and 4-point or more improvement in the itch numeric rating scale (NRS), using originating study baseline data. Itch data were collected during the first 16 weeks in BREEZE-AD3. The last originating study visit was the first BREEZE-AD3 visit; therefore, data are presented for continuous weeks of therapy, including the 16-week originating study period. Missing data were imputed by last observation carried forward. Modified intention-to-treat analysis was used. RESULTS: Of the responder/partial responder population, the proportion of patients treated with baricitinib, 4 mg (n = 70) (mean [SD] age, 36.7 [15.5] years; 42 [60%] were men), achieving vIGA-AD (0,1) at week 16 was 45.7% (BREEZE-AD3 baseline) and, at week 68, 47.1%. Improvement of 75% or more in the EASI score was 70.0% at week 16 and 55.7% at week 68. The proportion of patients achieving an itch NRS improvement greater than or equal to 4 points at week 16 was 52.5% and, at week 32, 45.9%. Of the responder/partial responder population, the proportion of patients treated with baricitinib, 2 mg (n = 54) (mean [SD] age, 32.8 [12.7] years; 28 [51.9%] were men), achieving vIGA-AD (0,1) at week 16 was 46.3% and, at week 68, 59.3%. Improvement in the EASI75 score was 74.1% at week 16 and 81.5% at week 68. The proportion of patients achieving an itch NRS improvement greater than or equal to 4 points at week 16 was 44.2% and, at week 32, 39.5%. CONCLUSIONS AND RELEVANCE: In this long-term double-blind extension study of 2 randomized clinical trials, baricitinib, 4 and 2 mg, demonstrated sustained long-term efficacy in patients with moderate to severe atopic dermatitis. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT03334435.

Temporary interruption of baricitinib: characterization of interruptions and effect on clinical outcomes in patients with rheumatoid arthritis.

BACKGROUND: In clinical practice, temporary interruption of rheumatoid arthritis (RA) therapy is common for various reasons including side effects, non-compliance, or necessity for surgery. To characterize temporary interruptions of baricitinib and placebo-matched tablets in phase 3 studies of patients with moderate-to-severe rheumatoid arthritis (RA) and describe their impact on efficacy and safety. METHODS: During 4 baricitinib phase 3 studies, investigators documented timing, reason, and duration of investigator-initiated temporary interruptions of study drug. In 2 studies, patients recorded RA symptoms in daily diaries for 12 weeks. Post hoc analyses investigated changes in symptom scores during interruptions and resumption of treatment. Interruptions were evaluated for reoccurrence of adverse events or laboratory abnormalities after retreatment. RESULTS: Across the placebo-controlled studies, interruptions occurred in larger proportions of baricitinib- (2 mg, 18%; 4 mg, 18%) vs placebo-treated (9%) patients in only one study (bDMARD-inadequate responder patients, RA-BEACON). In the active comparator-controlled studies, the lowest rates of interruption were in the baricitinib monotherapy arm (9%) of RA-BEGIN (vs methotrexate monotherapy or combination therapy), and proportions were similar for baricitinib (10%) and adalimumab (9%) in RA-BEAM. Adverse events were the most common reason for interruption, but their reoccurrence after drug restart was infrequent. Most interruptions lasted ≤ 2 weeks. Daily diaries indicated modest symptom increases during interruption with return to pre-interruption levels or better after resumption. Interruptions had no impact on long-term efficacy outcomes. CONCLUSIONS: Consistent with its pharmacologic properties, brief interruptions of baricitinib during phase 3 studies were associated with minor increases in RA symptoms that resolved following retreatment. This analysis provides useful information for clinicians, as temporary interruption of antirheumatic therapy is common in the care of patients with RA. TRIAL REGISTRATION: ClinicalTrials.gov; NCT01710358, NCT01711359, NCT01721057, NCT01721044.

Correction to: Temporary interruption of baricitinib: characterization of interruptions and effect on clinical outcomes in patients with rheumatoid arthritis.

An amendment to this paper has been published and can be accessed via the original article.

Safety Profile of Baricitinib in Patients with Active Rheumatoid Arthritis with over 2 Years Median Time in Treatment.

OBJECTIVE: Baricitinib is an oral, once-daily selective Janus kinase (JAK1/JAK2) inhibitor for adults with moderately to severely active rheumatoid arthritis (RA). We evaluated baricitinib's safety profile through 288 weeks (up to September 1, 2016) with an integrated database [8 phase III/II/Ib trials, 1 longterm extension (LTE)]. METHODS: The "all-bari-RA" group included patients who received any baricitinib dose. Placebo comparison was based on the 6 studies with 4 mg and placebo up to Week 24 ("placebo-4 mg" dataset). Dose response assessment was based on 4 studies with 2 mg and 4 mg including LTE data ("2 mg-4 mg-extended"). The uncommon events description used the non-controlled all-bari-RA. RESULTS: There were 3492 patients who received baricitinib for 6637 total patient-years (PY) of exposure (median 2.1 yrs, maximum 5.5 yrs). No differences in rates of death, adverse events leading to drug discontinuation, malignancies, major adverse cardiovascular event (MACE), or serious infections were seen for 4 mg versus placebo or for 4 mg versus 2 mg. Infections including herpes zoster were significantly more frequent for 4 mg versus placebo. Deep vein thrombosis/pulmonary embolism were reported with 4 mg but not placebo [all-bari-RA incidence rate (IR) 0.5/100 PY]; the IR did not differ between doses (0.5 vs 0.6/100 PY, 2 mg vs 4 mg, respectively) or compared to published RA rates. All-bari-RA had 6 cases of lymphoma (IR 0.09/100 PY), 3 gastrointestinal perforations (0.05/100 PY), 10 cases of tuberculosis (all in endemic areas; 0.15/100 PY), and 22 all-cause deaths (0.33/100 PY). IR for malignancies (0.8/100 PY) and MACE (0.5/100 PY) were low and did not increase with prolonged exposure. CONCLUSION: In this integrated analysis of patients with moderate to severe active RA with exposure up to 5.5 years, baricitinib has an acceptable safety profile in the context of demonstrated efficacy. Trial registration numbers: NCT01185353, NCT00902486, NCT01469013, NCT01710358, NCT01721044, NCT01721057, NCT01711359, and NCT01885078 at clinicaltrials.gov.

Effect on platelet reactivity from a prasugrel loading dose after a clopidogrel loading dose compared with a prasugrel loading dose alone: Transferring From Clopidogrel Loading Dose to Prasugrel Loading Dose in Acute Coronary Syndrome Patients (TRIPLET): a randomized controlled trial.

BACKGROUND: Adding a prasugrel loading dose (LD) to a clopidogrel LD could be desirable because clopidogrel may fail to provide adequate levels of platelet inhibition in patients with acute coronary syndrome undergoing percutaneous coronary intervention. METHODS AND RESULTS: The pharmacodynamic response of prasugrel 60 mg ld alone was compared with prasugrel 60 mg or 30 mg added 24 hours to clopidogrel 600 mg in Transferring From Clopidogrel Loading Dose To Prasugrel Loading Dose In Acute Coronary Syndrome Patients study: a multicenter, randomized, double-blind, double-dummy, 3-arm, parallel, active-comparator controlled study. Two hundred eighty-two patients were randomized to 3 LD strategies: placebo plus prasugrel 60 mg, clopidogrel 600 mg plus prasugrel 60 mg, or clopidogrel 600 mg plus prasugrel 30 mg. Platelet function was assessed using VerifyNow P2Y12 Reaction Units (PRU) immediately before prasugrel LD, and 2, 6, 24, and 72 hours after prasugrel LD in 149 patients with evaluable platelet function studies. At 6 hours after the prasugrel 60 mg LD, the least squares mean (95% confidence interval) difference between placebo/prasugrel 60 mg and clopidogrel 600 mg/prasugrel 60 mg (primary outcome) was 22.2 (-11.0 to 55.5; P=0.19; least squares mean PRU 57.9 versus 35.6, respectively). For clopidogrel 600 mg/prasugrel 30 mg (least squares mean PRU, 53.9), the difference was 3.9 (-28.2 to 36.1; P=0.81) versus placebo/prasugrel 60 mg. No significant differences in PRU were observed at any time point across the 3 groups. There were few bleeding events observed regardless of treatment. CONCLUSIONS: Platelet reactivity with prasugrel 60 mg LD added to clopidogrel 600 mg LD was not significantly different compared with prasugrel 60 mg LD alone in acute coronary syndrome patients undergoing percutaneous coronary intervention. CLINICAL TRIAL REGISTRATION URL: http://www.clinicaltrials.gov. Unique identifier: NCT01115738.