KRT-232 Versus Best Available Therapy for the Treatment of Subjects With Myelofibrosis Who Are Relapsed or Refractory to JAK Inhibitor Treatment (BOREAS)
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ClinicalTrials.gov Identifier: NCT03662126 |
Recruitment Status :
Recruiting
First Posted : September 7, 2018
Last Update Posted : April 28, 2023
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This study evaluates KRT-232, a novel oral small molecule inhibitor of MDM2, for the treatment of patients with myelofibrosis (MF) who no longer benefit from treatment with a JAK inhibitor. Inhibition of MDM2 is a novel mechanism of action in MF.
This study will be conducted in 2 phases. Phase 2 will determine the KRT-232 recommended dose and dosing schedule; Phase 3 will test KRT-232 vs Best Available Therapy (BAT). Patients in the Phase 3 part of the study will be randomized 2:1 to receive either KRT-232 (Arm 1) or BAT (Arm 2). The BAT administered will be determined by the treating physician, with the option to "cross-over" to KRT-232 treatment after 6 months of BAT or if the disease worsens at any time.
Condition or disease | Intervention/treatment | Phase |
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Primary Myelofibrosis (PMF) Post-Polycythemia Vera MF (Post-PV-MF) Post-Essential Thrombocythemia MF (Post-ET-MF) | Drug: KRT-232 Drug: Best Available Therapy (BAT) | Phase 2 Phase 3 |
Study Type : | Interventional (Clinical Trial) |
Estimated Enrollment : | 385 participants |
Allocation: | Randomized |
Intervention Model: | Crossover Assignment |
Masking: | Single (Outcomes Assessor) |
Primary Purpose: | Treatment |
Official Title: | A Phase 2/3 Randomized, Controlled, Open-Label Study of KRT 232 in Subjects With Primary Myelofibrosis (PMF), Post Polycythemia Vera MF (Post-PV-MF), Or Post Essential Thrombocythemia MF (Post-ET-MF) Who Are Relapsed or Refractory to Janus Kinase (JAK) Inhibitor Treatment |
Actual Study Start Date : | January 15, 2019 |
Estimated Primary Completion Date : | December 31, 2023 |
Estimated Study Completion Date : | December 31, 2025 |

Arm | Intervention/treatment |
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Experimental: Part A Cohort 1
KRT-232 120 mg by mouth once daily for Days 1-7, off treatment for Days 8-21 (21-day cycles)
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Drug: KRT-232
KRT-232, administered by mouth |
Experimental: Part A Cohort 2
KRT-232 240 mg by mouth once daily for Days 1-7, off treatment for Days 8-21 (21-day cycles)
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Drug: KRT-232
KRT-232, administered by mouth |
Experimental: Part A Cohort 3
KRT-232 240 mg by mouth once daily for Days 1-7, off treatment for Days 8-28 (28-day cycles)
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Drug: KRT-232
KRT-232, administered by mouth |
Experimental: Part A Cohort 4b
KRT-232 240 mg by mouth once daily for Days 1-5, off treatment for Days 6-28 (28-day cycles)
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Drug: KRT-232
KRT-232, administered by mouth |
Experimental: Part B Arm 1 KRT-232
KRT-232 240 mg by mouth once daily for Days 1-7, off treatment for Days 8-28 (28-day cycles)
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Drug: KRT-232
KRT-232, administered by mouth |
Active Comparator: Part B Arm 2 Best Available Therapy
Best available therapy at the discretion of the investigator, on a 28-day cycle.
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Drug: Best Available Therapy (BAT)
Best available therapy options include:
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- (Part A Only) Spleen Volume Reduction (SVR) [ Time Frame: 24 weeks ]The proportion of subjects achieving a ≥ 35% spleen volume reduction (SVR) from Baseline to Week 24, as assessed by magnetic resonance imaging (MRI) or computed tomography (CT) scan
- (Part B Only) Spleen Volume Reduction (SVR) [ Time Frame: 24 Weeks ]The proportion of subjects achieving SVR of ≥ 35% at Week 24 by MRI/CT scan (central review)
- (Part A only) Improvement in Total Symptom Score (TSS) [ Time Frame: 48 weeks ]The proportion of subjects who have at least a 50% reduction from Baseline to Week 24 and Week 48 in the total symptom score as measured by the modified MPN-SAF v2.0
- (Part B only) Improvement of Total Symptom Score (TSS) [ Time Frame: 24 Weeks ]The proportion of subjects who have at least a 50% reduction from Baseline to Week 24 in the total symptom score as measured by the MF-SAF v4.0
- (Part B only) Overall Survival (OS) [ Time Frame: 48 months ]Time from randomization to death from any cause
- (Part B only) Progression free survival (PFS) [ Time Frame: 48 months ]Time from randomization to either first occurrence of disease progression or death due to any cause
- (Part B Only) Overall Spleen Volume Reduction (SVR) [ Time Frame: 48 months ]The proportion of subjects in each arm achieving SVR of ≥ 35% at any time by MRI/CT scan (central review)
- (Part B Only) Spleen Response Duration [ Time Frame: 48 months ]Time from initial SVR of ≥ 35% by MRI/CT (central review) until the first occurrence of disease progression
- (Part B Only) Rate of conversion from RBC transfusion dependent to independent [ Time Frame: 24 weeks ]The proportion of subjects who have RBC transfusion independence at week 24

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Ages Eligible for Study: | 18 Years and older (Adult, Older Adult) |
Sexes Eligible for Study: | All |
Accepts Healthy Volunteers: | No |
Inclusion Criteria:
- Confirmed diagnosis of PMF, post-PV MF or post-ET MF (WHO)
- High, intermediate-2, or intermediate-1 risk Dynamic International Prognostic System (DIPSS)
- Failure of prior treatment with JAK inhibitor
- ECOG ≤ 2
Exclusion Criteria:
- Prior splenectomy
- Splenic irradiation within 3 months prior to randomization
- History of major hemorrhage or intracranial hemorrhage within 6 months prior to randomization
- History of stroke, reversible ischemic neurological defect or transient ischemic attack within 6 months prior to randomization
- Prior MDM2 inhibitor therapy or p53-directed therapy
- Prior allogeneic stem-cell transplant or plans for allogeneic stem cell transplant
- History of major organ transplant
- Grade 2 or higher QTc prolongation (> 480 milliseconds per NCI-CTCAE criteria, version 5.0)

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.
Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT03662126
Contact: John Mei | 650-542-0136 | jmei@kartosthera.com | |
Contact: Yulia Khalina | 908-656-2799 | ykhalina@kartosthera.com |

Responsible Party: | Kartos Therapeutics, Inc. |
ClinicalTrials.gov Identifier: | NCT03662126 |
Other Study ID Numbers: |
KRT-232-101 |
First Posted: | September 7, 2018 Key Record Dates |
Last Update Posted: | April 28, 2023 |
Last Verified: | April 2023 |
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 |
navtemadlin |
Polycythemia Vera Primary Myelofibrosis Polycythemia Thrombocytosis Thrombocythemia, Essential Myeloproliferative Disorders Bone Marrow Diseases Hematologic Diseases |
Bone Marrow Neoplasms Hematologic Neoplasms Neoplasms by Site Neoplasms Blood Platelet Disorders Blood Coagulation Disorders Hemorrhagic Disorders |