Evaluation of Avatrombopag for the Treatment of Thrombocytopenia in Japanese Adults With Chronic ITP

An Open-label Study to Evaluate the Efficacy and Safety of Avatrombopag for the Treatment of Thrombocytopenia in Japanese Adults With Chronic Immune Thrombocytopenia

Evaluate the efficacy, safety, and PK of avatrombopag given for 26 weeks in Japanese adults with chronic immune thrombocytopenia (ITP).

Study Overview

• Status: Completed
• Conditions: Immune Thrombocytopenia
• Intervention / Treatment: Drug: Avatrombopag Oral Tablet

Detailed Description

This Phase 3, multicenter, open label study will evaluate the efficacy, safety, and population pharmacokinetics (PK) of avatrombopag in Japanese adults with chronic ITP. At least 19 subjects will be enrolled. The study will consist of 3 phases: Pre-enrollment, Primary Investigation, and Extension Phase until market authorization in Japan.

• Study Type: Interventional
• Enrollment (Actual): 19
• Phase: Phase 3

Contacts and Locations

Study Locations

• Japan
  • Aichi-ken
    • Toyohashi, Aichi-ken, Japan, 441-8570
      • Sobi Site 105
  • Ehime
    • Tōon, Ehime, Japan, 791-0295
      • Sobi Site 110
  • Fukuoka
    • Iizuka-shi, Fukuoka, Japan, 820-8505
      • Sobi Site 118
    • Kitakyushu, Fukuoka, Japan, 802-8555
      • Sobi Site 116
    • Kurume, Fukuoka, Japan, 830-8543
      • Sobi Site 117
  • Gifu
    • Gifu, Gifu, Japan, 500-8513
      • Sobi Site 114
  • Hiroshima
    • Fukuyama-shi, Hiroshima, Japan, 720-2121
      • Sobi Site 115
    • Hiroshima, Hiroshima, Japan, 730-0052
      • Sobi Site 109
  • Hyōgo
    • Kobe, Hyōgo, Japan, 650-0047
      • Sobi Site 108
  • Ishikawa-ken
    • Kanazawa, Ishikawa-ken, Japan, 920-8650
      • Sobi Site 113
  • Iwata
    • Shiwa-gun, Iwata, Japan, 028-3695
      • Sobi Site 101
  • Kanagawa
    • Fujisawa, Kanagawa, Japan, 251-8550
      • Sobi Site 111
  • Kumamoto
    • Kumamoto, Kumamoto, Japan, 862-8655
      • Sobi Site 119
  • Osaka
    • Hirakata, Osaka, Japan, 573-1191
      • Sobi Site 107
    • Suita, Osaka, Japan, 565-0871
      • Sobi Site 106
  • Tokyo
    • Hachiōji-shi, Tokyo, Japan, 192-0032
      • Sobi Site 104
  • Toyko
    • Bunkyō City, Toyko, Japan, 113-8603
      • Sobi Site 103
  • Yamanashi
    • Chuo-shi, Yamanashi, Japan, 409-3898
      • Sobi Site 102
    • Kofu, Yamanashi, Japan, 400-8506
      • Sobi Site 112

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Subject has a confirmed diagnosis of chronic immune thrombocytopenia (ITP) (≥12 months duration) and has had an insufficient response to a previous ITP treatment, in the opinion of the Investigator.
• Subject has an average of 2 platelet counts <30×10^9/L (no single count can be >35×10^9/L). The 2 samples must be obtained ≥48 hours and ≤2 weeks apart.

Exclusion Criteria:

• Subjects with known secondary immune thrombocytopenia (e.g., with known Helicobacter pylori-induced ITP, subjects infected with known human immunodeficiency virus (HIV) or hepatitis C virus (HCV) or subjects with known systemic lupus erythematosus).
• Subjects with known inherited thrombocytopenia (e.g., Myosin Heavy Chain 9 (MYH-9) disorders) or hereditary thrombophilic disorders (e.g., Factor V Leiden, antithrombin III deficiency).
• History of myelodysplastic syndrome (MDS).
• History of arterial or venous thrombosis.
• Subjects with a history of significant cardiovascular disease (e.g., congestive heart failure (CHF) New York Heart Association Grade III/IV, arrhythmia known to increase the risk of thromboembolic events [e.g., atrial fibrillation], angina, coronary artery stent placement, angioplasty, coronary artery bypass grafting).
• Subjects with a history of cirrhosis, portal hypertension, or chronic active hepatitis.
• Subjects with concurrent malignant disease or receiving cytotoxic chemotherapy for a reason other than ITP treatment.
• Use of immunoglobulins (IVIg and anti-D) or corticosteroid rescue therapy within 1 week of Day 1/Baseline.
• Splenectomy or use of rituximab within 12 weeks of Day 1/Baseline.
• Use of romiplostim or eltrombopag within 1 week of Day 1/Baseline.
• Use of chronic corticosteroid treatment or azathioprine within 4 weeks of Day 1/Baseline, unless receiving a stable dose for at least 4 weeks.
• Use of mycophenolate mofetil, cyclosporin A, or danazol within 4 weeks of Day 1/Baseline, unless receiving a stable dose for at least 12 weeks.
• Use of cyclophosphamide or vinca alkaloid regimens within 4 weeks of Baseline Visit.
• Currently receiving moderate or strong dual inhibitors/inducers of CYP2C9 and CYP3A4.
• Serum creatinine ≥1.5× the upper limit of normal (ULN).
• Serum bilirubin ≥2×ULN.
• Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) ≥3×ULN.
• Females who are pregnant (positive beta-human chorionic gonadotropin (β-hCG) test) or breastfeeding.
• Received treatment with an investigational drug within 30 days or 5 half-lives (whichever is longer) before Day 1/Baseline.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Other: Avatrombopag; Avatrombopag 20 mg oral tablet	Drug: Avatrombopag Oral Tablet; Avatrombopag 20 mg given once daily (initial dose). Dosage adjustments were determined by the physician to maintain a platelet count between 50 x 10^9 to 200 x 10^9 as defined in the protocol and in accordance with overseas labeling.; Other Names: Doptelet

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Cumulative Number of Weeks of Platelet Response	Cumulative number of weeks in which the platelet count is ≥50×10^9/L during 26 weeks of treatment in the absence of rescue therapy.	26 weeks of active treatment

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Response Rate at Day 8	Proportion of subjects with a platelet response ≥50×10^9/L at Day 8 in the absence of rescue therapy	Day 8

Collaborators and Investigators

• Sponsor: Sobi, Inc.

Publications and helpful links

General Publications

• Yamaguchi H, Iino M, Tomiyama Y, Kamiya H, Zhang J, Skuban N. (2025, October 10-12). One-year efficacy and safety of avatrombopag for chronic immune thrombocytopenia in Japanese adults [Conference presentation abstract]. 87th Annual Meeting of the Japanese Society of Hematology, Kobe, Hyogo, Japan.
• Yamaguchi H, Iino M, Kowata S, Yamamoto R, Yamanouchi J, Imamura Y, Kirito K, Yokoyama K, Ito T, Ishikawa T, Shiratsuchi M, Tomiyama Y, Kamiya H, Zhang J, Jamieson BD. Correction: A phase 3 study of the efficacy and safety of avatrombopag in Japanese adults with chronic immune thrombocytopenia. Int J Hematol. 2025 Oct;122(4):623. doi: 10.1007/s12185-025-04054-5. No abstract available.
• Yamaguchi H, Iino M, Kowata S, Yamamoto R, Yamanouchi J, Imamura Y, Kirito K, Yokoyama K, Ito T, Ishikawa T, Shiratsuchi M, Tomiyama Y, Kamiya H, Zhang J, Jamieson BD. A phase 3 study of the efficacy and safety of avatrombopag in Japanese adults with chronic immune thrombocytopenia. Int J Hematol. 2025 Oct;122(4):521-532. doi: 10.1007/s12185-025-04001-4. Epub 2025 May 20.

Study record dates

Study Major Dates

• Study Start (Actual): June 15, 2022
• Primary Completion (Actual): January 17, 2024
• Study Completion (Actual): October 29, 2025

Study Registration Dates

• First Submitted: April 21, 2022
• First Submitted That Met QC Criteria: May 5, 2022
• First Posted (Actual): May 11, 2022

Study Record Updates

• Last Update Posted (Actual): June 3, 2026
• Last Update Submitted That Met QC Criteria: May 15, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: ITP
• Additional Relevant MeSH Terms: Cytopenia; Pathologic Processes; Autoimmune Diseases; Immune System Diseases; Hemorrhage; Skin Manifestations; Hematologic Diseases; Blood Coagulation Disorders; Hemorrhagic Disorders; Blood Platelet Disorders; Thrombotic Microangiopathies; Purpura, Thrombocytopenic; Purpura; Thrombocytopenia; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Hemic and Lymphatic Diseases; Purpura, Thrombocytopenic, Idiopathic; avatrombopag
• Other Study ID Numbers: AVA-ITP-307

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: Yes