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Frespaciguat

Phase 2

Pulmonary Hypertension | Small molecule | Cardiovascular |Merck & Company, Inc.|Last Updated: May 1, 2026

Success Probability

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Market & Valuation

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Trial Design

RandomizedDouble-BlindPLACEBO_CONTROLLED
Total Trials2
Total Enrollment151

FDA Designations

No designations recorded

Clinical trial landscape

Frespaciguat · 4 trials · 4 indications

Phase 2 2Phase 1 2
NCT05612035Frespaciguat (MK-5475) INSIGNIA-PH-COPD: A Study of the Efficacy and Safety of Frespaciguat (an Inhaled sGC Stimulator) in Adults With PH-COPDPulmonary Hypertension
ACTIVE NOT_RECRUITING129 Analytics
NCT04732221A Study of the Efficacy and Safety of Frespaciguat (MK-5475) in Participants With Pulmonary Arterial Hypertension (INSIGNIA-PAH: Phase 2/3 Study of an Inhaled sGC Stimulator in PAH) (MK-5475-007)Pulmonary Arterial Hypertension
COMPLETED168 Analytics
PHASE2ACTIVE NOT_RECRUITING
Frespaciguat (MK-5475) INSIGNIA-PH-COPD: A Study of the Efficacy and Safety of Frespaciguat (an Inhaled sGC Stimulator) in Adults With PH-COPD
Pulmonary HypertensionUnlock trial analytics
PHASE2COMPLETED
A Study of the Efficacy and Safety of Frespaciguat (MK-5475) in Participants With Pulmonary Arterial Hypertension (INSIGNIA-PAH: Phase 2/3 Study of an Inhaled sGC Stimulator in PAH) (MK-5475-007)
Pulmonary Arterial HypertensionUnlock trial analytics

Study Endpoints

Primary Endpoints

Mean Change From Baseline in 6-minute Walk Distance (6MWD) at Week 24
Baseline and Week 24

6MWD is assessed using the 6-minute walk test (6MWT).

Phase 2 Cohort: Mean Percent Change From Baseline in Pulmonary Vascular Resistance (PVR) at 12 Weeks
At baseline and 12 weeks

PVR was calculated in participants after MK-5475 dosing at baseline and Week 12. PVR is assessed by right heart catheterization (RHC). Based on the variables obtained by right heart catheterization (RHC), the percentage change from baseline PVR was calculated. Per protocol, this outcome measure was assessed only for base period and was not assessed during extension period.

Phase 3 Cohort: Mean Change From Baseline in 6-Minute Walk Distance (6MWD) at 12 Weeks
At baseline and 12 weeks

6MWD is measured by an exercise test known as 6-Minute Walk Test (6MWT) that assesses functional capacity. It measures the distance covered over a time of 6 minutes and is intended to be used as an outcome measure by which to compare changes in excercise capacity. Each participant's 6MWD is to be measured at baseline and at 12 weeks. An increase in the distance walked during the 6MWT indicates improvement in functional exercise capacity.

Percentage of Participants Who Experienced at Least 1 Adverse Event (AE)
Up to approximately 139 days

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention. The percentage of participants who experienced an AE was assessed.

Percentage of Participants Who Discontinued Study Drug Due to an AE
Up to approximately 32 days

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention. The number of participants who discontinued treatment due to an AE was assessed.

Percentage Change From Baseline to Day 28 in Pulmonary Vascular Resistance (PVR): Part 2
Baseline (between Day -5 and Day -1) and Day 28

PVR was calculated in participants after MK-5475 dosing at baseline and Day 28. Based on the variables obtained by right heart catheterization (RHC), the fold change from baseline individual PVR was calculated. The difference from baseline was assessed on the log scale and then back-transformed for reporting (percent change from baseline). Per protocol, this outcome measure was only assessed during the Part 2 and was not assessed during part 1.

Number of Participants Who Experienced at Least 1 Adverse Event (AE): All Parts
Up to ~14 days after last dose of treatment period (Up to ~32 weeks total)

An AE was defined as any untoward medical occurrence in a participant which may not necessarily have a causal relationship with the treatment. An AE could therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease that was temporally associated with use of a medicinal product, regardless of whether or not it was considered related to the medicinal product. The number of participants who experienced at least 1 AE was reported by dose separately for Part 1 plus Part 2 Period 1, for the RHC Period, and for the FRI Period.

Number of Participants Who Discontinued From the Study Due to an AE: All Parts
Up to ~14 days after last dose of treatment period (Up to ~32 weeks total)

An AE was defined as any untoward medical occurrence in a participant which may not necessarily have a causal relationship with the treatment. An AE could therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease that was temporally associated with use of a medicinal product, regardless of whether or not it was considered related to the medicinal product. The number of participants who discontinued from the study due to an AE was reported by dose separately for Part 1 plus Part 2 Period 1, for the RHC Period, and for the FRI Period.

Percentage Change From Baseline in Minimum Pulmonary Vascular Resistance (PVR): Part 2 Right Heart Catheterization (RHC) Period
Baseline: Pre-dose on Day 1 of RHC Period (up to 185 days) and up to 4.5 hours post-dose

For each participant in the RHC Period, the percentage change from baseline for the minimum post-dose PVR value over the duration of the RHC procedure was calculated. The average of pre-dose measurements was set as the baseline. Mean (SD) percent change from baseline in PVR minimum were calculated and reported for each dose group that underwent RHC in Part 2. Per protocol, this outcome measure was only assessed during the Part 2 RHC Period for each panel and was not assessed during Part 1.

Secondary Endpoints

Mean Change From Baseline in 6MWD at Week 12
Baseline and Week 12
Mean Change From Baseline in N-Terminal Pro B-Type Natriuretic Peptide (NT-proBNP) at Week 12
Baseline and Week 12
Mean Change From Baseline in NT-ProBNP at Week 24
Baseline and Week 24
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Study Design & Arms

AllocationRANDOMIZED
MaskingTRIPLE
ModelPARALLEL
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
FrespaciguatEXPERIMENTALParticipants with PH-COPD will receive 380 µg of frespaciguat as an oral inhalation once daily for 24 weeks (base period) and thereafter for up to 42 months (optional extension period).
PlaceboPLACEBO_COMPARATORParticipants with PH-COPD will receive matching placebo as an oral inhalation once daily for 24 weeks (base period) and then 380 µg of frespaciguat as an oral inhalation once daily for up to 42 months (optional extension period).
Phase 2 Cohort Frespaciguat 380 µgEXPERIMENTALParticipants receive frespaciguat 380 µg via oral inhalation once daily for 12 week base period and for optional 40 month extension period.
Phase 2 Cohort Frespaciguat 100 µgEXPERIMENTALParticipants receive frespaciguat 100 µg via oral inhalation once daily for 12 week base period and for optional 40 month extension period.
Phase 2 Cohort Frespaciguat 32 µgEXPERIMENTALParticipants receive frespaciguat 32 µg via oral inhalation once daily for 12 week base period and for optional 40 month extension period.
Phase 2 Cohort PlaceboPLACEBO_COMPARATORParticipants receive placebo via oral inhalation once daily for 12 week base period, and one of the MK-5475 doses (380, 100, or 32 µg) for the optional 40 month extension period.
Phase 3 Cohort FrespaciguatEXPERIMENTALParticipants receive one of 3 frespaciguat doses (380, 100 or 32 µg) to be selected at end of the Phase 2 Cohort, administered via oral inhalation once daily for 12-week base period and up to 40 months in the extension period
Phase 3 Cohort PlaceboPLACEBO_COMPARATORParticipants receive placebo via oral inhalation once daily for 12 week base period and up to 40 months in the extension period.
Part 1: FrespaciguatEXPERIMENTALParticipants receive frespaciguat 360 μg once daily (QD) via inhalation from Days 1-7. Following review of pharmacokinetic (PK) and safety data, a second 7 days of dosing may be initiated. A dose of up to 360 μg up to twice a day may be administered based on PK data in these participants.
Part 1: PlaceboPLACEBO_COMPARATORParticipants receive placebo QD via inhalation from Days 1-7.
Part 2: FrespaciguatEXPERIMENTALParticipants receive frespaciguat 32 µg, 100 µg, 195 µg or 380 μg QD via inhalation from Days 1-28.
Part 2: PlaceboPLACEBO_COMPARATORParticipants receive placebo QD via inhalation from Days 1-28.
Panel A: Frespaciguat 120 ug/165 ug/240 ug/240 ug/240 ug (Parts 1 and 2)EXPERIMENTALParticipants in Panel A will receive a single inhaled dose of frespaciguat 120 ug in Period 1 of Part 1, followed by frespaciguat 165 ug in Period 2, followed by frespaciguat 240 ug in Period 3. Each dose will be separated by at least a 7-day washout. In Part 2 Period 2, participants will receive a single inhaled dose of frespaciguat 240 ug and undergo a right heart catheterization (RHC). In Part 2 Period 3, participants will receive a single inhaled dose of frespaciguat 240 ug and undergo a functional respiratory imaging (FRI).
Panel B: 300 ug/360 ug/360 ug (Part 2)EXPERIMENTALParticipants in Panel B will receive a single inhaled dose of frespaciguat 300 ug in Period 1 of Part 2. In Period 2 of Part 2, participants will receive a single inhaled dose of frespaciguat 360 ug and undergo FRI. In Period 3 of Part 2, participants receive a single inhaled dose of frespaciguat 360 ug and undergo RHC. Each dose will be separated by at least a 7-day washout.
Panel C: 300 ug/360 ug/360 ug (Part 2, Expansion)EXPERIMENTALParticipants in Panel C will receive a single inhaled dose of frespaciguat 300 ug in Period 1 of Part 2. In Period 2 of Part 2, participants will receive a single inhaled dose of frespaciguat 360 ug and undergo FRI. In Period 3 of Part 2, participants receive a single inhaled dose of frespaciguat 360 ug and undergo RHC. Each dose will be separated by at least a 7-day washout.
Panel D: 480 ug/120 ug/120 ug (Part 2)EXPERIMENTALParticipants in Panel D will receive a single inhaled dose of frespaciguat 480 ug in Period 1 of Part 2. In Period 2 of Part 2, participants will receive a single inhaled dose of frespaciguat 120 ug and undergo FRI. In Period 3 of Part 2, participants receive a single inhaled dose of frespaciguat 120 ug and undergo RHC. Each dose will be separated by at least a 7-day washout.
Placebo (Part 1)PLACEBO_COMPARATORParticipants will receive a single inhaled dose of matching placebo in Part 1.

Interventions

NameTypeDescription
FrespaciguatDRUGFrespaciguat 380 µg administered as dry powder inhalation once daily.
PlaceboDRUGPlacebo administered as dry powder inhalation once daily.
Placebo to FrespaciguatDRUGPlacebo administered as dry powder inhalation
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Eligibility Criteria

Age Range40 Years to 85 Years
SexALL
Healthy VolunteersNo
Study Sites85

The key inclusion and exclusion criteria include but are not limited to the following: Inclusion Criteria: * Has Group 3.1 pulmonary hypertension chronic obstructive pulmonary disease (PH-COPD) as defined by the Clinical Classification of Pulmonary Hypertension. * Has a right heart catheterization...

Countries:United StatesArgentinaAustraliaAustriaBelgiumColombiaFranceGermanyGuatemalaIsraelItalyMexicoPeruSouth AfricaSouth KoreaSpainSwitzerlandTurkey (Türkiye)United KingdomCanadaGreeceNew ZealandPolandRussiaSwedenMoldova
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Recent Changes (Last 90 Days)

LOWMay 26, 2026NCT05612035Enrollment: 120 → 129
LOWMay 24, 2026NCT05612035studyFirstPostDate: changed

Frequently asked questions about Frespaciguat

What is Frespaciguat used for?

Frespaciguat is an investigational small molecule being developed for pulmonary arterial hypertension and pulmonary hypertension. It is being studied in conditions including pulmonary hypertension associated with chronic obstructive pulmonary disease. The drug is administered by inhalation and is currently in Phase 2 clinical development.

How does Frespaciguat work?

Frespaciguat is an inhaled soluble guanylate cyclase (sGC) stimulator. It works by stimulating sGC, an enzyme that plays a role in the nitric oxide signaling pathway, which can lead to vasodilation. This mechanism is being studied for its potential to reduce pulmonary vascular resistance in patients with pulmonary hypertension.

Who makes Frespaciguat?

Frespaciguat is being developed by Merck & Company, Inc., which trades under the ticker symbol MRK. The company is conducting clinical trials to evaluate the drug's efficacy and safety in patients with pulmonary arterial hypertension and pulmonary hypertension associated with chronic obstructive pulmonary disease.

What phase is Frespaciguat in?

Frespaciguat is in Phase 2 clinical development. It has completed Phase 1 and Phase 2 trials, including the INSIGNIA-PAH study, and an additional Phase 2 trial for pulmonary hypertension associated with chronic obstructive pulmonary disease is active but not recruiting participants.

What clinical trials is Frespaciguat in?

Frespaciguat has been studied in several clinical trials, including NCT03744637 and NCT04370873, both Phase 1 studies that are completed. The Phase 2 INSIGNIA-PAH trial (NCT04732221) is completed, and the Phase 2 INSIGNIA-PH-COPD trial (NCT05612035) is active but not recruiting. These trials evaluate the drug in pulmonary arterial hypertension and PH-COPD.

Is Frespaciguat the same as MK-5475?

Yes, Frespaciguat is also known as MK-5475. Clinical trials reference the drug under both names, such as the INSIGNIA-PAH study (MK-5475-007) and the INSIGNIA-PH-COPD study (MK-5475-008). Both names refer to the same investigational inhaled sGC stimulator.