Background: The CoStar stent is a novel cobalt chromium stent designed specifically for drug delivery. The COSTAR I trial represents the first-in-man study of the CoStar Paclitaxel-Eluting Coronary Stent System evaluating three dose release formulations of paclitaxel in a bioresorbable polymer matrix in the treatment of de novo coronary lesions.
Methods: The COSTAR I Trial was a prospective, multi-center registry enrolling 87 patients in four Indian centers for treatment of up to two de novo lesions = 25 mm in length in a reference vessel 2.5-3.5 mm in diameter. Three dose release formulations were studied: 30 microg eluted over 10 days bidirectionally (Group 1, n =10), 10 microg eluted over 30 days abluminally (Group 2, n=40) and 3 microg eluted over 30 days abluminally (Group 3, n = 37).
Results: Demographics and lesion characteristics were similar between the groups and treatment in all three groups included small caliber vessels (RVD 2.45 +/- 0.30 - 2.57 +/- 0.36 mm). The primary endpoint of in-stent late loss at four months was lowest in Group 2 (0.43 +/- 0.43 mm) compared to Group 1 and Group 3 (0.51 +/- 7 mn; 0.74 mm and 1.07 +/- 0.65 mm respectively). In-segment late loss followed similar trends, being lowest in Group 2 (0.24 +/- 0.39 mm) compared to Groups 1 and 3 (0.52 +/- 0.66 mm and 0.76 +/- 0.57 mm respectively). Group 2 demonstrated better angiographic out-comes at 12 months with in-stent late loss of 0.55 +/- 0.38 mm when compared to Groups 1 and 3 (0.90 +/- 0.76 mm and 0.74 +/- 0.55 mm respectively). Cumulative binary restenosis rates at twelve months were 1.9%, 35.7% and 39.1% in Groups 2, 1 and 3 respectively. Clinical outcomes trended similarly with cumulative MACE rates at twelve months being lowest at 7.5% in Group 2 as compared to 20% in Group 1 and 21.6% in Group 3 respectively.
Conclusions: In this first-in-man feasibility trial, angiographic and clinical results seen with the extended release formulation at a higher dose (10 microg/30 days) demonstrate the feasibility of the CoStar stent platform in the treatment of native coronary lesions. It also demonstrates the importance of drug dose and release kinetics.