Robert Roscigno

Efficacy and safety of treprostinil: an epoprostenol analog for primary pulmonary hypertension.

Intravenous epoprostenol is currently FDA approved for management of primary pulmonary hypertension, but it requires intravenous infusion and is associated with adverse effects. The objective of this study was to evaluate the effects of an epoprostenol analog, treprostinil, for management of pulmonary hypertension. Ten tertiary care academic institutions with pulmonary hypertension programs participated in these pilot trials. In the first trial, intravenous epoprostenol and intravenous treprostinil were compared. In the second trial, intravenous treprostinil and subcutaneous treprostinil were compared. In the third trial, subcutaneous treprostinil was compared with placebo infusion during an 8-week period. Intravenous epoprostenol and intravenous treprostinil resulted in a similar reduction in pulmonary vascular resistance acutely (22% and 20%, respectively). Intravenous treprostinil and subcutaneous treprostinil also demonstrated comparable short-term decrease in pulmonary vascular resistance (23% and 28%, respectively). The placebo-controlled 8-week trial demonstrated a mean improvement of 37 ± 17 m as measured by the 6-minute walk distance in patients receiving treprostinil compared with a 6 ± 28 m reduction in those receiving placebo. There were trends toward an improvement in cardiac index and pulmonary vascular resistance index in the treprostinil group. Subcutaneous treprostinil has favorable hemodynamic effects when given acutely and in the short term. Treprostinil can be given safely to an ambulatory patient with a novel subcutaneous delivery pump system.

Absolute Bioavailability and Pharmacokinetics of Treprostinil Sodium Administered by Acute Subcutaneous Infusion

The objective of this study was to evaluate the absolute bioavailability and acute pharmacokinetics of treprostinil sodium administered by continuous, short‐term subcutaneous infusion in normal subjects. Fifteen healthy volunteers received treprostinil via an intravenous infusion at 15 ng/kg/ min over 150 minutes, followed by a 5‐ to 7‐day washout and a subcutaneous infusion at the same rate administered over 150 minutes. Serial plasma samples were collected predosing, during dosing, and postdosing, and plasma treprostinil concentration levels were measured by a validated liquid chromatography atmospheric pressure ionization tandem mass spectrometry (LC/MS/MS) method with a lower limit of quantitation (LLOQ) of 25 pg/mL. Acute administration of treprostinil administered by subcutaneous infusion at a rate of 15 ng/kg/min for 150 minutes achieved a mean Cmax of 1.47 ng/mL. Mean AUC∞ values for intravenous and subcutaneous dosing were 3.52 and 3.97 ng•h/mL, respectively, resulting in a mean apparent absolute bioavailability of 113% for subcutaneous administration. It was possible that the area under of the curve for the intravenous administration was underestimated because most of the terminal elimination phase could not be documented due to the LLOQ of the assay. The mean apparent elimination half‐life of treprostinil following subcutaneous administration was 1.38 hours, compared to 0.87 hours following intravenous administration. It was concluded that treprostinil administered by subcutaneous administration is completely absorbed, with a slightly longer half‐life compared to intravenously administered treprostinil.

Pharmacokinetics of treprostinil sodium administered by 28-day chronic continuous subcutaneous infusion.

The objective of this study was to assess the pharmacokinetics and safety of treprostinil sodium administered as a 28‐day continuous subcutaneous infusion at escalating infusion rates of 2.5 to 15 ng/kg/min in normal subjects. Fourteen healthy adult volunteers received a 28‐day continuous subcutaneous infusion of treprostinil at escalating infusion rates of 2.5, 5, 10, and 15 ng/kg/min. Doses were escalated every 7 days with no washouts between escalations. Serial plasma samples were collected predosing, during dosing, and postdosing. Samples were also collected every 3 hours on Day 7 of each dosing period to evaluate diurnal variation over a 24‐hour steady‐state interval. Plasma treprostinil concentration was measured by a validated liquid chromatography atmospheric pressure ionization tandem mass spectrometry (LC/MS/MS) method with a lower limit of quantitation (LLOQ) of 25 pg/mL. Distinct steady states were achieved for each of the four treprostinil doses. Linear regression analysis of mean steady‐state treprostinil concentration versus targeted dose yielded a fitted line with an r2 of 0.92. Variation in apparent plasma clearance for the four doses was small (i.e., 9.77–10.4 mL/kg/min). Consistent diurnal cycles of two peak and two trough treprostinil concentrations were observed over a 24‐hour steady‐state interval for each dose with peak levels 20% to 30% higher than trough levels. The terminal half‐life of treprostinil was 2.93 hours. Intersubject variability for mean pharmacokinetic parameters was small (coefficients of variation ranging from 13.6%–25.5%). At clinically relevant doses, the pharmacokinetics of treprostinil were linear and dose independent with modest, consistent diurnal cycles consisting of two daily peaks and two daily troughs observed for all four doses. In addition, the elimination half‐life was about 3 hours.