Open-label Extension Study to Evaluate the Long-term Safety and Tolerability of Aficamten in Adults With HCM (FOREST-HCM)

January 20, 2026 updated by: Cytokinetics

A Follow-Up, Open-Label, Research Evaluation of Sustained Treatment With Aficamten (CK-3773274) in Hypertrophic Cardiomyopathy (HCM)

The purpose of this study is to collect long-term safety and tolerability data for aficamten.

Study Overview

Status

Enrolling by invitation

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

900

Phase

  • Phase 2
  • Phase 3

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Argentina
      • Buenos Aires, Argentina, C1428
        • Instituto Cardiovascular de Buenos Aires(ICBA)
  • Australia
      • Bedford Park, Australia, 5042
        • Flinders Medical Centre, Cardiology Research
      • Chermside, Australia, 4032
        • The Prince Charles Hospital
      • Murdoch, Australia, 6150
        • Fiona Stanley Hospital, AHF Unit
  • Brazil
      • São Paulo, Brazil, 04012-909
        • Instituto Dante Pazzanese de Cardiologia
  • Canada
      • Edmonton, Canada, T5H 3V9
        • Royal Alexandra Hospital
      • Halifax, Canada, B3H 3A7
        • QEII Health Science Centre (Halifax Infirmary site)
    • Quebec
      • Québec, Quebec, Canada, G1V 4G5
        • Institut Universitaire de Cardiologie et de Pneumologie de Québec-Université Laval
  • Czechia
      • Prague, Czechia, 128 08
        • Il. Interni klinika kardiologie a angiologie
  • Denmark
      • Aalborg, Denmark, 9000
        • Department of Cardiology Aalborg University Hospital
      • Aarhus, Denmark, 8200
        • Department of Cardiology Aarhus University Hospital
      • Copenhagen, Denmark, 2100
        • The Heart Center, Department of Cardiology
      • Copenhagen, Denmark, 2400
        • Copenhagen University Hospital
      • Odense, Denmark, 5000
        • Odense University Hospital
  • France
      • Marseille, France, 130005
        • Hopital de la Timone Service de cardiologie
      • Montpellier, France, 34295
        • CHU Montpellier - Hôpital Arnaud de Villeneuve
      • Montpellier, France, 340000
        • Clinique du Millénaire
      • Nantes, France, 44093
        • CHU de Nantes Institut Du Thorax et du systeme nerveux Clinique Cardiologique et des Maladies Vasculaires
      • Paris, France, 75015
        • Hôpital Européen Georges Pompidou
      • Paris, France, 75010
        • Hopital Lariboisière
      • Pessac, France, 33604
        • Hopital cardiologique de Haut-Leveque
      • Rennes, France, 35033
        • Centre hospitalier universitaire (CHU) de Rennes-Hopital Pontchaillou
      • Toulouse, France, 31059
        • Centre Hospitalier universitaire de Toulouse - Rangueil Hospital
  • Germany
      • Berlin, Germany, 13353
        • Charite-Universitaetsmedizin Berlin
      • Essen, Germany, 45147
        • Universitaetsklinikum Essen
      • Goettigen, Germany, 37075
        • Universitaetsmedizin Goettingen Klinik fur Kardiologie und Pneumologie
      • Heidelberg, Germany, 69120
        • Universitaesklinkum Heidelberg
      • Jena, Germany, 07747
        • Universitaetsklinikum Jena
      • Würzburg, Germany, 97078
        • Universitaetskinikum Wuerzburg Deutsches Zentrum fur Herzinsuffzienz Wurzburg (DZHI) Comprehensive Heart Failure Center (CHFC)
  • Greece
      • Athens, Greece, 10676
        • Evangelismos General Hospital of Athens
      • Athens, Greece, 11527
        • "Hippokration" General Hospital of Athens
      • Athens, Greece, 17674
        • Onassis Hospital
      • Attiki, Greece, 12462
        • University General Hospital "Attikon"
  • Hungary
      • Budapest, Hungary, 1122
        • Semmelweis Egyetem Varosmajori Sziv es Ergyogyaszati Klinika
      • Szeged, Hungary, 6725
        • Szegedi Tudományegyetem, Belgyógyászati Klinika, Kardiológiai Központ
  • Iceland
      • Reykjavik, Iceland, 101
        • Landspitali University Hospital
  • Israel
      • Ashkelon, Israel, 7830604
        • The Barzilai University Medical Center
      • Jerusalem, Israel, 9112001
        • Hadassah Medical Center- Ein Kerem
      • Kfar Saba, Israel, 4428164
        • Meir Medical Center
      • Ramat Gan, Israel, 5265601
        • The Chaim Sheba Medical Center
      • Safed, Israel, 1311001
        • Ziv Medical Center
  • Italy
      • Florence, Italy, 50134
        • Unit Cardiomiopatie, Dipartimento Cardio ToracoVascolare
      • Milan, Italy, 20097
        • IRCCS Policlinico San Donato
      • Milan, Italy, 20162
        • Asst Grande Ospedale Metropolitano Niguarda
      • Napoli, Italy, 80131
        • Azienda Ospedaliera Universitaria Federico II di Napoli
      • Pisa, Italy, 56124
        • Fondazione toscana Gabriele Monesterio per la ricarca medica Dipartimento Cardiotoracico UOC Cardiologia e Medicina Cardiovasculare Ospedale San Cataldo
      • Roma, Italy, 00189
        • Dipartimento di Medicina Clinica e Molecolare Universita Sapienza di Roma Unita di Terapia Intensiva Cardiologica Azienda Ospedaliero Universitaria Sant'Andrea
      • Trieste, Italy, 34149
        • Azienda Sanitaria Universitaria Giuliano Isontina
  • Netherlands
      • Amsterdam, Netherlands, 1105
        • Amsterdam UMC
      • Maastricht, Netherlands, 6229 HX
        • Maastricht University Medical Center (MUMC)
      • Rotterdam, Netherlands, 3015
        • Erasmus Medical Center Department of Cardiology
  • Poland
      • Katowice, Poland, 40-555
        • Kardio Brynow S.C.
      • Warsaw, Poland, 04-628
        • Narodowy Instytut Kardiologii Stefana Kardynala Wyszynskiego - Panstwowy Instytut Badawczy Centrum Zaburzen Rytmu Serca
  • Portugal
      • Aveiro, Portugal, 3814-501
        • Centro Hospitalar Do Baixo Vouga, EPE Cardiology Department
      • Lisbon, Portugal
        • Hospital da Luz
      • Lisbon, Portugal, 1998-018
        • Hospital Cuf Descobertas S.A.
      • Lisbon, Portugal, 1150-199
        • Unidade Local De Saude De Sao Jose E.P.E
  • Spain
      • A Coruña, Spain, 15006
        • Complejo Hospitalario Universitario A Coruña
      • Barcelona, Spain, 08036
        • Hospital Clinic Barcelona
      • Madrid, Spain, 28040
        • Hospital Clinico Universitario San Carlos
      • Madrid, Spain, 28220
        • Hospital Universitario Puerta de Hierro Majadahonda
      • Madrid, Spain, 28007
        • Hospital General Universitario Gregorio Maranon (HGUGM)
      • Madrid, Spain, 30120
        • Hospital Clínico Universitario Virgen de la Arrixaca
      • Málaga, Spain, 29010
        • Hospital Universitario Virgen de la Victoria
      • Palma, Spain, 07198
        • Hospital Universitario Son Llatzer
      • Pontevedra, Spain, 36312
        • Complexo Hospitalario Universitario de Vigo
      • Salamanca, Spain, 37007
        • Hospital Universitario de Salamanca
      • Seville, Spain, 41013
        • Hospital Universitario Virgen del Rocio
      • Seville, Spain, 41009
        • Hospital Universitario Virgen Macarena-merge
  • United Kingdom
      • Birmingham, United Kingdom, B15 2GW
        • Queen Elizabeth Hospital Birmingham University Hospitals Birmingham NHS Foundation Trust
      • Dundee, United Kingdom, DD2 1SG
        • Ninewells Hospital and Medical School
      • Glasgow, United Kingdom, G51 4TF
        • Glasgow Clinical Research Facility Neuroscience Institute
      • Liverpool, United Kingdom, L14 3PE
        • Liverpool Heart and Chest Hospital
      • London, United Kingdom, EC1A 7BE
        • St Bartholomew's Hospital
      • London, United Kingdom, SW3 6NP
        • Royal Brompton Hospital
      • London, United Kingdom, SW17 0QT
        • St George's University Hospitals NHS Foundation Trust
      • Oxford, United Kingdom, OX3 9DU
        • Oxford Centre for Clinical Magnetic Resonance Research (OCMR) Division of Cardiovascular Medicine Radcliffe Department of Medicine University of Oxford
  • United States
    • Alabama
      • Birmingham, Alabama, United States, 35233
        • University of Alabama at Birmingham
    • Alaska
      • Anchorage, Alaska, United States, 99508
        • Alaska Heart and Vascular Institute
    • Arizona
      • Phoenix, Arizona, United States, 85054
        • Mayo Clinic Building - Phoenix
    • California
      • La Jolla, California, United States, 92037
        • UC San Diego Health - Sulpizio Cardiovascular Center
      • Los Angeles, California, United States, 90048
        • Cedars-Sinai Medical Center (Smidt Heart Institute)
      • Los Angeles, California, United States, 90048
        • Cedar-Sinai Medical Center
      • San Francisco, California, United States, 94143
        • UCSF Medical Center
    • Connecticut
      • New Haven, Connecticut, United States, 06519
        • Yale New Haven Hospital
    • District of Columbia
      • Washington D.C., District of Columbia, United States, 20010
        • Medstar Washington Hospital Center
    • Florida
      • Fort Lauderdale, Florida, United States, 33308
        • Holy Cross Hospital / Cardiology Associates
    • Georgia
      • Atlanta, Georgia, United States, 30322
        • Emory Clinic
      • Fayetteville, Georgia, United States, 30214
        • Piedmont Fayette Hospital
    • Illinois
      • Evanston, Illinois, United States, 60208
        • Northwestern University
    • Kansas
      • Kansas City, Kansas, United States, 66160
        • The University of Kansas Medical Center
    • Massachusetts
      • Boston, Massachusetts, United States, 02115
        • Brigham and Women's Hospital
      • Boston, Massachusetts, United States, 02114
        • Massachusetts General Hospital
      • Burlington, Massachusetts, United States, 01805
        • Lahey Hospital & Medical Center
    • Michigan
      • Ann Arbor, Michigan, United States, 48109
        • Michigan Medicine - University of Michigan
      • Ann Arbor, Michigan, United States, 48109
        • University of Michigan Health System (UMHS) - University Hospital (University of Michigan Medical Center)
      • Detroit, Michigan, United States, 48202
        • Henry Ford Hospital
    • Missouri
      • Kansas City, Missouri, United States, 64111
        • Saint Luke's Hospital of Kansas City
    • New Jersey
      • Morristown, New Jersey, United States, 07960
        • Morristown Medical Center
    • New York
      • Manhasset, New York, United States, 11030
        • Northwell Health North Shore University Hospital
      • New York, New York, United States, 10016
        • NYU Langone Health
      • New York, New York, United States, 10021
        • Weill Cornell Medicine
      • New York, New York, United States, 10029
        • Mount Sinai Hospital
      • New York, New York, United States, 10032
        • Columbia University Medical Center/New York Presbyterian Hospital
      • Valhalla, New York, United States, 10595
        • Westchester Medical Center
    • North Carolina
      • Charlotte, North Carolina, United States, 28204
        • Sanger Heart & Vascular Institute - HCM Clinic
      • Durham, North Carolina, United States, 27710
        • Duke Cardiology at Southpoint
    • Ohio
      • Cincinnati, Ohio, United States, 45219
        • The Linder Research Center at The Christ Hospital
      • Cleveland, Ohio, United States, 44195
        • Cleveland Clinic
      • Cleveland, Ohio, United States, 44106
        • University Hospitals Cleveland Medical Center
    • Oklahoma
      • Tulsa, Oklahoma, United States, 76104
        • Ascension St. John Clinical Research Institute
    • Oregon
      • Portland, Oregon, United States, 97239
        • Oregon Health & Science University
      • Portland, Oregon, United States, 97225
        • Providence St. Vincent Medical Center
    • Pennsylvania
      • Philadelphia, Pennsylvania, United States, 19104
        • Hospital of the University of Pennsylvania (University of Pennsylvania School of Medicine)
      • Pittsburgh, Pennsylvania, United States, 15213
        • UPMC Presbyterian
    • South Carolina
      • Charleston, South Carolina, United States, 29425
        • Medical University of South Carolina
      • Greenville, South Carolina, United States, 29605
        • Greenville Memorial Hospital
    • Tennessee
      • Nashville, Tennessee, United States, 37232
        • Vanderbilt University Medical Center
      • Nashville, Tennessee, United States, 37205
        • Ascension Saint Thomas Heart West
    • Texas
      • Dallas, Texas, United States, 75390
        • The University of Texas Southwestern Medical Center at Dallas
      • Houston, Texas, United States, 77030
        • Houston Methodist Hospital
      • Houston, Texas, United States, 77030
        • CHI St. Luke's Health Baylor College of Medicine Medical Center
    • Utah
      • Murray, Utah, United States, 84107
        • Intermountain Medical Center
      • Salt Lake City, Utah, United States, 84132
        • University of Utah Health
    • Virginia
      • Charlottesville, Virginia, United States, 22908
        • University of Virginia Health System University Hospital
      • Falls Church, Virginia, United States, 22042
        • Inova Health Care Services
    • Washington
      • Seattle, Washington, United States, 98101
        • Virginia Mason Medical Center
    • West Virginia
      • Morgantown, West Virginia, United States, 26506
        • WVUMedicine
    • Wisconsin
      • Milwaukee, Wisconsin, United States, 53215
        • Aurora St. Luke's Medical Center

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years to 85 years (Adult, Older Adult)

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Completion of a Cytokinetics trial investigating aficamten
  • LVEF ≥ 55% at the Screening Visit

Exclusion Criteria:

  • Has received treatment with mavacamten: (a) within 56 days prior to dosing and (b) has not received approval for participation from the Medical Monitor.
  • Has participated in another investigational device or drug study or received an investigational device or drug < 1 month (or 5 half-lives for drugs, whichever is longer) prior to screening. Other investigational procedures while participating in this study are not permitted.

  • Since completion of a previous trial of aficamten has:

    • Developed new-onset paroxysmal or permanent atrial fibrillation requiring rhythm restoring treatment (eg, direct-current cardioversion, ablation procedure, or antiarrhythmic therapy) < 30 days prior to screening. Patient may re-screen for CY 6022 after 30 days if heart rate (HR) < 100 bpm and/or rhythm is stable > 30 days
    • Undergone septal reduction therapy (surgical myectomy or transcatheter alcohol ablation)
  • Had a confirmed LVEF < 40% with an associated dose interruption during participation in a prior study with aficamten
  • History of implantable ICD placement within 30 days prior to screening.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

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

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Aficamten up to 20 mg
Patients in this arm take daily dose of aficamten. Each patient will start at the lowest prespecified dose and titrate up to their maximum tolerated dose.
Drug: Aficamten (5 - 20 mg)
Aficamten tablets administered orally. During titration phase, clinic visits will occur approximately every 2-6 weeks. In the maintenance phase clinic visits will occur every 24 weeks, with safety check-in occurring every 12 weeks between visits by phone or, if desirable, in the clinic.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Incidence of adverse events observed during dosing of aficamten in patients with HCM
Time Frame: Baseline to End of study, up to 5 years
Patient incidence of reported Adverse Events (AEs)
Baseline to End of study, up to 5 years

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Incidence of serious adverse events observed during dosing of aficamten in patients with HCM
Time Frame: Baseline to End of study, up to 5 years
Patient incidence of reported Serious Adverse Events (SAEs)
Baseline to End of study, up to 5 years
Incidence of left ventricular ejection fraction (LVEF) < 50% observed during dosing of aficamten in patients with HCM
Time Frame: Baseline to End of study, up to 5 years
Patient incidence of reported LVEF <50%
Baseline to End of study, up to 5 years
Long-term effects of aficamten on left ventricular outflow tract gradient (LVOT G) in patients with oHCM
Time Frame: Baseline through the end of participation at 12-24 week intervals
Peak LVOT-G at rest; applicable only to patients with oHCM
Baseline through the end of participation at 12-24 week intervals
Long-term effects of aficamten on resting LVOT-G
Time Frame: Baseline through the end of participation at 12-24 week intervals
Proportion of patients with resting LVOT-G < 30 mmHg; applicable only to patients with oHCM
Baseline through the end of participation at 12-24 week intervals
Long-term effects of aficamten on post Valsalva LVOT-G
Time Frame: Baseline through the end of participation at 12-24 week intervals
Proportion of patients with post-Valsalva LVOT-G < 50 mmHg; applicable only to patients with oHCM
Baseline through the end of participation at 12-24 week intervals
Long-term effects of aficamten on post Valsalva LVOT-G
Time Frame: Baseline through the end of participation at 12-24 week intervals
Proportion of patients with post-Valsalva LVOT-G < 30 mmHg; applicable only to patients with oHCM
Baseline through the end of participation at 12-24 week intervals
Long-term effects of aficamten on left ventricular ejection fraction (LVEF) and post-Valsalva LVOT-G
Time Frame: Baseline through the end of participation at 12-24 week intervals
Proportion of patients with LVEF ≥ 50%, resting LVOT-G < 30 mmHg, and post-Valsalva LVOT-G < 50 mmHg; applicable only to patients with oHCM
Baseline through the end of participation at 12-24 week intervals
Long-term effects of aficamten on time to first resting LVOT-G < 30 mmHg through last follow-up
Time Frame: Time to the following event through last follow-up, up to 5 years
Applicable only to patients with oHCM
Time to the following event through last follow-up, up to 5 years
Long-term effects of aficamten on time to first post-Valsalva LVOT-G < 50 mmHg through last follow-up
Time Frame: Time to the following event through last follow-up, up to 5 years
Applicable only to patients with oHCM
Time to the following event through last follow-up, up to 5 years
Long-term effects of aficamten on time to first post-Valsalva LVOT-G < 30 mmHg through last follow-up
Time Frame: Time to the following event through last follow-up, up to 5 years
Applicable only to patients with oHCM
Time to the following event through last follow-up, up to 5 years
Long-term effects of aficamten on time to first LVEF ≥ 50%, resting LVOT-G < 30 mmHg, and post-Valsalva LVOT-G < 50 mmHg through last follow-up
Time Frame: Time to the following event through last follow-up, up to 5 years
Applicable only to patients with oHCM
Time to the following event through last follow-up, up to 5 years

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Cytokinetics

Investigators

  • Study Director: Cytokinetics, MD, Cytokinetics

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

May 6, 2021

Primary Completion (Estimated)

March 1, 2028

Study Completion (Estimated)

March 1, 2028

Study Registration Dates

First Submitted

April 9, 2021

First Submitted That Met QC Criteria

April 13, 2021

First Posted (Actual)

April 19, 2021

Study Record Updates

Last Update Posted (Actual)

January 22, 2026

Last Update Submitted That Met QC Criteria

January 20, 2026

Last Verified

January 1, 2025

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • CY 6022
  • 2020-003571-17 (EudraCT Number)
  • 2023-508963-58-00 (Other Identifier: EU CTR Number)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

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.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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