Procoagulant inhibitory properties of paclitaxel poliglumex

John Nemunaitis^1,2,3, Neil Senzer^1,2,3, Barry Cooper^2,3, Michael Nemunaitis¹, Cynthia Bedell¹, Jack W Singer⁴, Fred B Oldham^4
1Mary Crowley Cancer Research Centers, Dallas, TX, USA; ²Baylor Sammons Cancer Center, Dallas, TX, USA; ³Texas Oncology, Dallas, TX, USA; ⁴Cell Therapeutics, Inc., Seattle, WA, USA

Background: In Phase I evaluation of CT-2103 (paclitaxel poliglumex), prolongation of prothrombin time (PT) and activated thromboplastin time (aPTT) was observed, without clinical consequence, with doses 1.3–1.5 times higher than the current clinical dose of 175 mg/m². This Phase I, open-label, nonrandomized pilot study was performed to study the effect of the standard dose regimen on blood coagulation.
Methods: Seven previously treated solid tumor patients received CT-2103 175 mg/m² intravenously on day 1 of 21-day cycles for a mean of 5.4 cycles (median 4, range 2–14). Plasma samples were collected for cycle 1 predose and at hours 1, 24, 48, and 72 after the end of administration for drug levels, and for PT and aPTT assays.
Results: No coagulopathy-related adverse events were documented. Bleeding time remained normal in the six patients tested, with transient increases in PT and aPTT noted but resolving within 72 hours. Titration studies at 100 µg/mL of CT-2103 (corresponding to the standard clinical dose) prolonged PT and aPTT clotting times, produced a modest dose-dependent reduction of thrombin and factor Xa, and no significant changes in factors IXa, XIa, or XIIa. Two patients achieved stable disease for ≥10 cycles.
Conclusion: CT-2103 is associated with transient prolongation of PT and aPTT without clinical sequelae.

Keywords: CT-2103, paclitaxel, poliglumex, cancer