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CYT387

Phase 4FDA approved

Primary Myelofibrosis | Small molecule | Oncology |GSK plc|Trials Updated: Aug 10, 2026

CYT387 development status

FDA approval on record Approved
Highest phase Phase 4 (NCT07498205)
Phase scored for GSKPhase 1
Registered trials 21 across 7 sponsors since Jul 2009

CYT387 target and mechanism

ModalitySmall molecule

Also known as Momelotinib, MMB, GS-0387, Momelotinib (MMB)

Success Probability

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Market & Valuation

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Trial Design

UNCONTROLLED
Total Trials13
Total Enrollment1,836

FDA Designations

No designations recorded

CYT387 clinical trials

CYT387 · 13 trials · 18 indications

Phase 3 3Phase 2 8Phase 1 2
NCT04173494A Study of Momelotinib Versus Danazol in Symptomatic and Anemic Myelofibrosis Participants (MOMENTUM)Primary Myelofibrosis
COMPLETED195 Analytics
NCT02101268Efficacy of Momelotinib Versus Best Available Therapy in Anemic or Thrombocytopenic Subjects With Primary Myelofibrosis (MF), Post-polycythemia Vera MF, or Post-essential Thrombocythemia MFPrimary Myelofibrosis (PMF)
COMPLETED156 Analytics
NCT01969838Momelotinib Versus Ruxolitinib in Subjects With MyelofibrosisPrimary Myelofibrosis
COMPLETED432 Analytics
PHASE3COMPLETED
A Study of Momelotinib Versus Danazol in Symptomatic and Anemic Myelofibrosis Participants (MOMENTUM)
Primary MyelofibrosisUnlock trial analytics
PHASE3COMPLETED
Efficacy of Momelotinib Versus Best Available Therapy in Anemic or Thrombocytopenic Subjects With Primary Myelofibrosis (MF), Post-polycythemia Vera MF, or Post-essential Thrombocythemia MF
Primary Myelofibrosis (PMF)Unlock trial analytics
PHASE3COMPLETED
Momelotinib Versus Ruxolitinib in Subjects With Myelofibrosis
Primary MyelofibrosisUnlock trial analytics

Study Endpoints

Primary Endpoints

Total Symptom Score (TSS) Response Rate at Week 24
Baseline and Week 24

Myelofibrosis Symptom Assessment Form (MFSAF) TSS version (v) 4.0 response rate was defined as percentage of participants with a \>= 50 percent (%) reduction from Baseline in mean MFSAF TSS over consecutive 28-day period immediately before end of Week 24. TSS response rate was measured using MFSAF v4.0. MFSAF v4.0 comprises 7 domains representing 7 most relevant symptoms of myelofibrosis (MF) identified through existing participant and clinician-based evidence: fatigue,night sweats,pruritus,abdominal discomfort,pain under left ribs,early satietyand bone pain. Participants scored each symptom domain using an 11-point numeric rating scale ranging from 0(absent) to 10(worst imaginable). The MFSAF TSS was calculated as sum of scores of 7 domains for a possible range of scores of 0 to 70, with a higher TSS corresponding to more severe symptoms. A reduction from Baseline corresponded to a lessening of MF symptoms. Baseline was the last assessment done before or on the day of first dose date.

Splenic Response Rate at Week 24
Week 24

Splenic response rate at Week 24 is defined as the percentage of participants who achieved a spleen volume reduction of ≥ 35% from baseline at the Week 24 assessment as measured by MRI or CT.

ORR (Objective response rate) at Week 26
At Week 26

ORR is defined as the proportion of participants who have achieved complete response (CR) or partial response (PR) during the 26-week Primary Treatment Period.

Determination of the maximum tolerated dose of momelotinib
First 4-week cycle of momelotinib treatment

The maximum tolerated dose (MTD) is defined by a target dose-limiting toxicities (DLT) rate of 30%, assessed during the observation window by a 3+3 design. The 3+3 design will enroll a first cohort of 3 patients at the starting dose of 200 mg/d: * If 0 of the 3 patients at the dose of 200 mg/d experienced a DLT during the first 4-week cycle of momelotinib, the dose will escalate to 300 mg/d for the next cohort. * If 1 of the 3 patients at the dose of 200 mg/d has a DLT, a cohort of three additional patients will be treated at the same dose of 200 mg/d. * If \> 1 patient of the 3 patients at the dose of 200 mg/d have a DLT, the dose will de-escalate to 150 mg/d for the next cohort. The same process will be repeated until reaching the MTD. In total, between 6 and 18 patients will be enrolled during this safety run-in phase.

Clinical efficacy
During the 24 first weeks of momelotinib treatment

Determination of overall clinical response rate at 24 weeks after momelotinib initiation on VEXAS related symptoms (including complete (CR) or partial response (PR)) : * CR includes complete disappearance of symptoms related to systemic inflammation according to treating physician and daily dose of steroids ≤ 10 mg/d (equivalent prednisolone). * PR includes complete disappearance of symptoms related to systemic inflammation according to treating physician and reduction of at least 50% of daily dose steroids compared to baseline and/or daily dose of steroids \> 10 mg/d.

Percentage of participants with Red Blood Cells - transfusion independence (RBC-TI) for at least 12 weeks, rolling over 24 weeks
Up to 24 weeks

RBC-TI defined as not requiring RBC transfusions (except in the case of clinically overt bleeding). Percentage of participants with RBC-TI will be measured for any consecutive 12-week interval over 24-week duration.

Number of participants with Grade 3 Adverse events (AEs), AE leading to treatment discontinuation and AEs leading to dose modifications
Up to approximately 109 weeks
Maximum plasma concentration (Cmax) of momelotinib and major metabolite of momelotinib (M21)
Up to 24 weeks
Area under the plasma concentration versus time curve (AUC) of momelotinib and M21
Up to 24 weeks
Percentage of Participants with TI Response by Week 24
Up to Week 24

TI response is defined as not requiring red blood cell (RBC) transfusion (except in the case of clinically overt bleeding) for any ≥12-week interval.

Number of Participants Who Had Access to, and Received the Intervention
Participants will be assessed every 12 weeks until discontinuation. Participation in this extended access study has been an average of approximately 8 months.
Transfusion Independence Response by Week 24
From baseline to Week 24

The percentage of subjects who became transfusion independent for ≥ 12 weeks at any time on study. A subject was considered transfusion independent on study if no RBC transfusion occurred in any 12-week period during the 24-week treatment period.

Long Term Safety and Tolerability as Measured by the Incidence and Severity of Adverse Events and Clinical Laboratory Abnormalities
From the first dose of momelotinib in the parent study to 30 days following permanent discontinuation of momelotinib in Study GS-US-352-1154.

Long-term safety and tolerability profile of momelotinib based on safety data (adverse events and selected hematology and chemistry laboratory parameters) collected after the first dose of momelotinib in the parent study.

To determine the long term safety and tolerability of orally-administered CYT387 in patients with PMF or post-ET/PV MF following completion of core study CCL09101
Safety monitoring will be undertaken for all patients every 3 months
To obtain information on the long term effectiveness of orally-administered CYT387 in patients with PMF or post-ET/PV MF
Every three months

Measured by complete response (CR) rate, partial response (PR) rate and clinical improvement (CI) rate according to IWG-MRT consensus criteria

To determine the safety of momelotinib by characterization and relationship of adverse events, affects on vital signs and laboratory parameters, and QTc intervals as measured by electrocardiogram (ECG)
6 months
To determine maximum tolerated dose of momelotinib by characterization of Dose Limiting Toxicities
6 months
To confirm the half-life of momelotinib by pharmacokinetic analyses
6 months
To determine the efficacy of momelotinib by evaluation of spleen and liver size, disease related constitutional symptoms, transfusion dependence and anemia response.
6 months
Safety and tolerability, dose-limiting toxicities (DLTs) and maximum tolerated dose (MTD) of orally-administered CYT387 in patients with PMF or post-ET/PV MF.
Ongoing throughout therapy up until 30 days after last dose of CYT387
Objective Response Rate (ORR), as measured by complete response (CR) rate, partial response (PR) rate and clinical improvement (CI) rate according to International Working Group for Myelofibrosis Research and Treatment (IWG-MRT) consensus criteria
Baseline to study completion

The Objective Response Rate (ORR), as measured by complete response (CR) rate, partial response (PR) rate and clinical improvement (CI) rate according to International Working Group for Myelofibrosis Research and Treatment (IWG-MRT) is to be measured at the end of every cycle of therapy.

Pharmacokinetics of CYT387 in patients with PMF or post-ET/PV MF
Baseline to end of Cycle 1

The pharmacokinetics (PK) of CYT387 in patients with PMF or post-ET/PV MF is to be assessed on Day 1 and Day 28 in Cycle 1 of therapy

Secondary Endpoints

Percentage of Participants With Transfusion Independence (TI) at Week 24
Week 24
Splenic Response Rate (SRR) of >=25% at Week 24
Baseline and Week 24
Change From Baseline in MFSAF TSS at Week 24
Baseline and Week 24
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Study Design & Arms

AllocationRANDOMIZED
MaskingQUADRUPLE
ModelPARALLEL
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
MomelotinibEXPERIMENTALParticipants will receive momelotinib plus placebo to match danazol
DanazolACTIVE_COMPARATORParticipants will receive danazol plus placebo to match momelotinib
Arm 1: MomelotinibEXPERIMENTALParticipants will receive open-label momelotinib for 24 weeks during the randomized treatment phase, after which they will be eligible to receive momelotinib in an extended treatment phase for up to an additional 204 weeks.
Arm 2: Best Available Therapy (BAT)ACTIVE_COMPARATORParticipants in the BAT treatment arm will receive open-label treatment at doses and schedules determined by the investigator in accordance with standard of care. Therapy may be changed at any time during the study except during the screening period. After completion of the randomized treatment phase, participants will be eligible to receive momelotinib for the duration of the study during the extended treatment phase for up to 204 weeks.
RuxolitinibACTIVE_COMPARATORParticipants will receive ruxolitinib plus placebo to match momelotinib.
Momelotinib Dose level 1 + GlucocorticoidsEXPERIMENTALParticipants will receive momelotinib at dose level 1 along with glucocorticoids as a background therapy (prednisone or prednisolone). Due to adaptive design of the study, additional participants may be randomized to this arm in phase 3.
Momelotinib Dose level 2 + GlucocorticoidsEXPERIMENTALParticipants will receive momelotinib at dose level 2 along with glucocorticoids as a background therapy (prednisone or prednisolone). Due to adaptive design of the study, additional participants may be randomized to this arm in phase 3
Placebo + GlucocorticoidsPLACEBO_COMPARATORParticipants will receive momelotinib matched placebo along with glucocorticoids as a background therapy(prednisone or prednisolone). Due to adaptive design of the study, additional participants may be randomized to this arm in phase 3
Momelotinib treatmentEXPERIMENTALPatients will receive momelotinib.
Momelotinib dose level 1EXPERIMENTAL -
Momelotinib dose level 2EXPERIMENTAL -
Momelotinib + LuspaterceptEXPERIMENTALParticipants with transfusion dependent primary myelofibrosis or post- PV/ ET myelofibrosis that is JAKi naïve or JAKi experienced will receive momelotinib and luspatercept.
Cohort 1: Study GS-US-352-0101OTHERParticipants will continue to receive the same dosage regimen as in the previous MMB study GS-US-352-0101 until MMB receives regulatory approval and is commercially available, or development of the product ceases.
Cohort 2: Study GS-US-352-1214OTHERParticipants will continue to receive the same dosage regimen as in the previous MMB study GS-US-352-1214 until MMB receives regulatory approval and is commercially available, or development of the product ceases.
Cohort 3: Study GS-US-352-1154OTHERParticipants will continue to receive the same dosage regimen as in the previous MMB study GS-US-352-1154 until MMB receives regulatory approval and is commercially available, or development of the product ceases..
Cohort 4: Study SRA-MMB-301OTHERParticipants will continue to receive the same dosage regimen as in the previous MMB study SRA-MMB-301 until MMB receives regulatory approval and is commercially available, or development of the product ceases.
Cohort 1EXPERIMENTALParticipants previously enrolled in Study CCL09191E will receive momelotinib for approximately 4 years.
Cohort 2EXPERIMENTALParticipants previously enrolled in Study YM387-II-02 will receive momelotinib for approximately 4 years.
Cohort 3EXPERIMENTALParticipants previously enrolled in Study GS-US-354-0101 will receive momelotinib for up to 4 years. Cohort 3 was closed and all enrolled participants were discontinued from this study because parent Study GS-US-354-0101 was terminated.
Cohort 4EXPERIMENTALParticipants previously enrolled in Study GS-US-352-1672 will receive momelotinib for approximately 4 years.
CYT387EXPERIMENTAL -

Interventions

NameTypeDescription
MomelotinibDRUGMomelotinib tablets will be self-administered orally once daily
Placebo to match danazolDRUGDanazol placebo capsules will be self-administered orally twice daily
DanazolDRUGDanazol capsules will be self-administered orally twice daily
Placebo to match momelotinibDRUGMomelotinib placebo tablets will be self-administered orally once daily
Best Available Therapy (BAT)DRUGRegimens for BAT may include but are not limited to chemotherapy (eg hydroxyurea), anagrelide, corticosteroid, hematopoietic growth factor, immunomodulating agent, androgen, interferon, and may include no myelofibrosis treatment.
RuxolitinibDRUGRuxolitinib tablets administered orally twice daily
Placebo to match ruxolitinibDRUGPlacebo to match ruxolitinib tablets administered orally twice daily
GlucocorticoidsDRUGGlucocorticoids (prednisone or prednisolone) will be administered
PlaceboDRUGPlacebo will be administered
Momelotinib treatmentDRUGPatients included will receive momelotinib continuously until disease progression or loss of response, at physician's discretion.
LuspaterceptDRUGLuspatercept will be administered subcutaneously.
MMBDRUGTablet(s) administered orally once daily
CYT387DRUGFor the Part 1 dose-escalation portion of the study, patients will be assigned to dose levels in successive cohorts starting with a dose in the first cohort of 100 mg/day. CYT387 will be orally self-administered as a single daily dose beginning on Day 1 of the study, and thereafter at approximately the same time each day of the 28-day cycle. It is recommended that all doses be preceded by a 2-hour fast from food and beverages, and be followed by a 1-hour post-dose fast from food and beverages. Twenty additional patients will be assigned to a 150 mg BID (twice daily) dosing schedule. CYT387 will be orally self-administered twice-daily with doses approximately 10-12 hours apart beginning on Day 1 of the study, and thereafter at approximately the same times each day of the 28-day cycle. For the Part 2 dose confirmation portion of the study, patients will be assigned to either 150 mg or 300 mg QD (once daily) dose groups.
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Eligibility Criteria

Age Range18 Years to N/A
SexALL
Healthy VolunteersNo
Study Sites167

Inclusion Criteria: * Age \>= 18 years. * Confirmed diagnosis of PMF in accordance with the World Health Organization (WHO) 2016 criteria, or Post- polycythemia vera/essential thrombocythemia (PV/ET) MF in accordance with the International Working Group-Myeloproliferative Neoplasms Research and Tre...

Countries:United StatesAustraliaAustriaBelgiumBulgariaCanadaCzechiaDenmarkFranceGermanyHungaryIsraelItalyNew ZealandPolandRomaniaSingaporeSouth KoreaSpainSwedenTaiwanUnited KingdomJapanNetherlands
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Frequently asked questions about CYT387

What is CYT387 used for in Primary Myelofibrosis?

CYT387 is an investigational small molecule being studied for the treatment of Primary Myelofibrosis, as well as Post-Polycythemia Vera Myelofibrosis and Post-Essential Thrombocythemia Myelofibrosis. It is a targeted therapy designed to address the underlying disease process in these myeloproliferative conditions.

Who makes CYT387?

CYT387 is being developed by GSK plc, a global biopharmaceutical company listed on the stock exchange under the ticker symbol GSK. The company is conducting clinical research to evaluate the safety and efficacy of this investigational drug in patients with myelofibrosis.

What phase is CYT387 in?

CYT387 is in Phase 1 clinical development. It is an investigational drug, meaning it has not been approved by regulatory authorities and is still undergoing clinical trials to assess its safety and effectiveness in patients with Primary Myelofibrosis and related conditions.

What clinical trials is CYT387 in?

CYT387 has been studied in one completed clinical trial, registered as NCT00935987. This Phase 1 study evaluated the safety and efficacy of CYT387 in patients with Primary Myelofibrosis, Post-Polycythemia Vera Myelofibrosis, or Post-Essential Thrombocythemia Myelofibrosis, enrolling 166 participants across the United States, Australia, and Canada.

Is CYT387 the same as momelotinib?

Yes, CYT387 is also known as momelotinib. This alternative name is used in scientific literature and clinical trial registries to refer to the same investigational drug being developed by GSK plc for the treatment of myelofibrosis.