A Phase 1/2 interventional study of ALN-6400 and Placebo in Hereditary Hemorrhagic Telangiectasia, sponsored by Alnylam Pharmaceuticals. Active, not recruiting at 16 sites in 6 countries. Open to participants aged 18 Years and older, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-10-15.
Sponsored by Alnylam Pharmaceuticals · Phase 1/2, Interventional, and Treatment
The purpose of this study is to:
106 studies on the registry are indexed under Telangiectasia, Hereditary Hemorrhagic; 24 are open to participants now.
This study's enrollment of 89 is above the median of 33 across 61 interventional studies indexed under Telangiectasia, Hereditary Hemorrhagic.
Browse Telangiectasia, Hereditary Hemorrhagic studies →Alnylam Pharmaceuticals is the lead sponsor of 84 studies on the registry; 19 are open to participants now.
Of its 18 completed or terminated interventional studies of FDA-regulated products, 15 (83%) have results posted.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Part A:
Part B:
Exclusion Criteria -
Part A:
Part B:
Parts A and B:
Note: other protocol defined inclusion / exclusion criteria apply
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Two enzymes measured in a routine blood test of the liver. Higher levels can mean the liver is under strain or damaged. SGPT and SGOT are older names for ALT and AST.
Criteria usually give a limit as a multiple of the upper limit of normal (ULN), often higher when cancer has spread to the liver.
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
A yellow substance made when red blood cells are broken down, which the liver clears. A high level can mean a problem with the liver or the bile ducts.
Criteria often allow more for people with Gilbert’s syndrome, a harmless inherited condition that raises bilirubin.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
ALT and AST (liver enzymes)
Two enzymes measured in a routine blood test of the liver. Higher levels can mean the liver is under strain or damaged. SGPT and SGOT are older names for ALT and AST.
Criteria usually give a limit as a multiple of the upper limit of normal (ULN), often higher when cancer has spread to the liver.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ULN (upper limit of normal)
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis C tests
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis B tests
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
GFR and eGFR (kidney filtering)
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Bilirubin
A yellow substance made when red blood cells are broken down, which the liver clears. A high level can mean a problem with the liver or the bile ducts.
Criteria often allow more for people with Gilbert’s syndrome, a harmless inherited condition that raises bilirubin.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants will be administered a single dose of ALN-6400.
Drug: ALN-6400
Participants will be administered a single dose of placebo.
Drug: Placebo
Participants will be administered multiple doses of ALN-6400.
Drug: ALN-6400
Participants will be administered multiple doses of placebo.
Drug: Placebo
ALN-6400 will be administered subcutaneously (SC)
Placebo will be administered subcutaneously (SC)
Part A: Frequency of Adverse Events
Time frame: Up to Week 36
Part B: Frequency of Adverse Events
Time frame: Up to Week 96
Part A: Concentrations of ALN-6400 in Plasma
Time frame: Predose and up to 2 days postdose
Part A: Change from Baseline in Plasminogen (PLG) in Plasma Protein Levels
Time frame: Predose and up to Week 36 postdose
Part B: Change from Baseline in Plasminogen (PLG) in Plasma Protein Levels
Time frame: Screening and up to Week 96 postdose
Part A: Change from Baseline in Plasminogen (PLG) in Plasma Activity Levels
Time frame: Predose and up to Week 36 postdose
Part B: Change from Baseline in Plasminogen (PLG) in Plasma Activity Levels
Time frame: Part B: Screening and up to Week 96 postdose
Part B: Change from Baseline in Intensity-adjusted Epistaxis Duration
Intensity-adjusted epistaxis duration will be assessed using a daily patient epistaxis diary.
Time frame: Baseline up to Week 96
Part B: Change from Baseline in Epistaxis Severity Score (ESS) Scale
Validated bleeding scale in HHT scored between 0-10, higher scores indicate worse bleeding.
Time frame: Baseline up to Week 96
Part B: Change from Baseline in Epistaxis Duration
Epistaxis duration will be assessed using a daily patient epistaxis diary.
Time frame: Baseline up to Week 96
Part B: Change from Baseline in Epistaxis Frequency
Epistaxis frequency will be assessed using a daily patient epistaxis diary.
Time frame: Baseline up to Week 96
Part B: Change from Baseline in Epistaxis Intensity
Epistaxis intensity will be assessed using a daily patient epistaxis diary.
Time frame: Baseline up to Week 96
Part B: Change from Baseline in Epistaxis-free Days per Month
Epistaxis-free days per month will be assessed using a daily patient epistaxis diary.
Time frame: Baseline up to Week 96
Part B: Change from Baseline in Hematologic Support Score (HSS)
The HSS is a quantitative tool designed to longitudinally assess the red blood cells (RBC) and iron supplementation needs of patients with HHT and other chronic bleeding disorders.
Time frame: Baseline up to Week 96
Part B: Change from Baseline in Iron Infusions
Time frame: Baseline up to Week 96
Part B: Change from Baseline in Red Blood Cell (RBC) Infusions
Time frame: Baseline up to Week 96
Part B: Change from Baseline in Hemoglobin
Time frame: Baseline up to Week 96
Part B: Change from Baseline in Quality of Life Patient-reported Outcomes (QoL/PRO) assessed by Nasal Outcome Score for Epistaxis in Hereditary Hemorrhagic Telangiectasia (NOSE HHT) Score
HHT-specific QoL/PRO will be assessed using the NOSE HHT score. The NOSE HHT is a 29-item patient-reported, clinically validated outcome measure, with total scores ranging continuously from 0 to 4 with higher scores indicating worse scores.
Time frame: Baseline up to Week 84
Part B: Change from Baseline in QoL/PRO assessed by Modified Patient Global Impression of Severity (mPGI-S) Score
HHT-specific QoL/PRO will be assessed using the mPGI-S. The patient will respond to a single question, providing their global impression of change in their overall status and epistaxis experience.
Time frame: Baseline up to Week 84
Plan to share: Yes — Phase 2-4: Access to Anonymized individual participant data that support these results is made available 12 months after study completion and not less than 12 months after the product and indication have been approved in the United States (US) and/or the European Union (EU). Data will be provided contingent upon the approval of a research proposal and the execution of a data sharing agreement. Requests for access to data can be submitted via the website www.vivli.org.
No publications or documents are linked to this record.
Started Nov 2024 (actual). Primary completion is estimated for Jan 2028, 37 months after the start.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
This study is active, not recruiting, as verified in Oct 2026. You cannot join it, but the record below documents what was studied.
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Telangiectasia, Hereditary Hemorrhagic →