Clinical Characterization of a Novel Oral Thrombopoietin Mimetic LGD-4665 in Healthy Volunteers Demonstrate Safe and Sustained Increases in Platelet Counts with Flexible Dosing Choices for Phase II Trials

• Published in: Blood 2008-11, Vol.112 (11), p.3406-3406
• Main Authors: Dziewanowska, Zofia E., Kapil, Ram P., Zhang, J.K., Berg, Jolene K., Stevens, Victor J., Matsumoto, Richard M., Greenberg, Lisa, Morris, Maryanna Y.
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V112.11.3406.3406

LGD-4665, a new generation small molecule oral thrombopoietin (TPO) mimetic, increases platelet counts in a dose proportional manner, and is associated with a high safety margin in healthy subjects after single and multiple daily, or weekly doses. Phase I characterization of LGD-4665 has demonstrated comparable platelet profiles following daily or weekly dosing, minimal effects of food on absorption, and no drug interaction with CYP 3A4 substrates. These attributes have led to the design of Phase II studies with flexible dose regimens for immune thrombocytopenic purpura (ITP), Hepatitis C and myelodysplastic syndrome (MDS). Weekly dosing regimen for a supportive therapy such as LGD-4665 in thrombocytopenic patients is desirable for patient convenience, compliance and overlap with concomitant therapies including peg-interferon in hepatitis C and certain chemotherapeutic agents in cancer patients. LGD-4665's long elimination half-life of 90 hrs and sustained increases in platelet counts in the Phase I single or multiple daily dose trials suggested a weekly dosing regimen should be evaluated. A Phase-I study was designed to assess once weekly, oral dosing for safety, pharmacodynamics (PD; platelet response) and pharmacokinetics (PK). This was conducted in 23 healthy volunteers randomized to receive 30 mg, 45 mg or 60 mg capsules of LGD-4665 for up to 6 weeks. All three LGD-4665 doses demonstrated a sustained increase in platelet counts that was dose proportional following weekly administration. The mean maximum percentage increase in platelet counts were 36%, 71% and 81% at 30 mg, 45 mg and 60 mg, respectively. The platelet increase of 71% after a weekly dose of 45 mg was comparable to a 79% increase following daily dosing of 7.5 mg with a loading dose. Platelets responded more quickly following the higher weekly doses (45 mg and 60 mg), with counts approaching 50% above baseline values within two weeks, and reaching a plateau at 4 to 5 weeks. Platelet counts gradually returned to baseline within three weeks post-treatment. Food effects were tested in 16 normal subjects and showed only a minimal decrease (23%) in absorption in a cross-over study, and should have no significant clinical impact. In another Phase I study in 25 healthy subjects, there was no pharmacokinetic drug-drug interaction between LGD-4665 and simvastatin, a sensitive substrate for CYP 3A4. In Phase I studies, LGD-4665 was safe and well tolerated. Only a few adverse events (AEs), with major