A Phase 2 interventional study of ANX005 in Huntington Disease, sponsored by Annexon, Inc.. Completed at 6 sites in United States. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-08-25.
Sponsored by Annexon, Inc. · Phase 2, Interventional, and Treatment
This study is a multi-center, open-label study of intravenous (IV) ANX005 in participants with, or at risk for, manifest Huntington's Disease (HD).
The objective of this study is to evaluate the effects of IV ANX005 administered for up to 22 weeks in participants with, or at risk for, manifest HD.
Participants will receive induction dosing of ANX005 administered by IV infusion on Days 1 and 5 or 6, followed by maintenance dosing every 2 weeks through Week 22, with follow up visits on Weeks 24, 28, and 36.
All participants will be contacted (in clinic visit or phone call) 6 months after study completion.
293 studies on the registry are indexed under Huntington Disease; 54 are open to participants now.
This study's enrollment of 28 is below the median of 40 across 207 interventional studies indexed under Huntington Disease.
Browse Huntington Disease studies →Annexon, Inc. is the lead sponsor of 16 studies on the registry; 2 are open to participants now.
Of its 8 completed or terminated interventional studies of FDA-regulated products, 3 (38%) 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.
Exclusion Criteria:
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.
Periods have stopped for good: usually no period for 12 months in a row without another medical reason, sometimes confirmed by a blood test (FSH).
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.
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
The other ingredients in a medicine besides the active drug, such as fillers, colours or preservatives.
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 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.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
The protein in red blood cells that carries oxygen. A low level is anaemia, which can cause tiredness and breathlessness. Measured in g/dL or g/L (9 g/dL is 90 g/L).
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.
Postmenopausal
Periods have stopped for good: usually no period for 12 months in a row without another medical reason, sometimes confirmed by a blood test (FSH).
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.
Childbearing potential
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Autoimmune disease
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Excipients
The other ingredients in a medicine besides the active drug, such as fillers, colours or preservatives.
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 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.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hemoglobin (Hb)
The protein in red blood cells that carries oxygen. A low level is anaemia, which can cause tiredness and breathlessness. Measured in g/dL or g/L (9 g/dL is 90 g/L).
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.
Participants will receive induction dosing of ANX005 administered by IV infusion on Days 1 and 5 or 6, followed by maintenance dosing every 2 weeks (Weeks 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, and 22) with follow up visits on Weeks 24, 28, and 36.
Drug: ANX005
Intravenous Infusion
Number of Participants With Treatment-Emergent Adverse Events (TEAEs)
An adverse event (AE) was defined as any untoward medical occurrence that developed or worsened in severity during the conduct of a clinical study and does not necessarily have a causal relationship to study drug. Serious AEs (SAEs) included death, a life-threatening AE, inpatient hospitalization or prolongation of existing hospitalization, persistent or significant disability or, a congenital anomaly or birth defect, or an important medical event that jeopardized the participant and required medical intervention to prevent 1 of the outcomes listed in this definition. A TEAE was any AE with an onset on or after the day of infusion through Week 36 (end of study). AEs were graded per National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE): Grade: 1=Mild, 2=Moderate, 3=Severe or medically significant but not immediately life-threatening. A summary of serious and non-serious AEs regardless of causality is located in 'Reported Adverse Events module'.
Time frame: From first dose of study drug up to end of study (Week 36)
Actual Dose of ANX005 Administered on Day 1
Time frame: Day 1
Actual Dose of ANX005 Administered on Week 22
Time frame: Week 22
Area Under the Concentration Versus Time Curve From Time 0 to t (AUC0-t) of ANX005 at Day 1
Time frame: Pre-dose up to 4 hours post-dose on Day 1
CSF Free Complement Component 1q (C1q) at Day 1
Time frame: Predose at Baseline (Day 1)
Blood Free C1q at Day 1
Time frame: Predose at Baseline (Day 1)
Change From Baseline in Complement C4a in CSF at Week 24
Time frame: Baseline, Week 24
Change From Baseline in Complement C4a in CSF at Week 36
Time frame: Baseline, Week 36
Change From Baseline in CSF NfL Level at Week 24
Time frame: Baseline, Week 24
Change From Baseline in CSF NfL Level at Week 36
Time frame: Baseline, Week 36
Change From Baseline in Blood NfL Level at Week 24
Time frame: Baseline, Week 24
Change From Baseline in Blood NfL Level at Week 36
Time frame: Baseline, Week 36
| Milestone | ANX005 |
|---|---|
| Started | 28 |
| Received at least 1 dose of study drug | 28 |
| Per protocol set | 23 |
| Pharmacokinetic (pk) analysis set | 28 |
| Completed | 25 |
| Not completed | 3 |
| Withdrew: Withdrawal by subject | 1 |
| Withdrew: Adverse event | 2 |
An adverse event (AE) was defined as any untoward medical occurrence that developed or worsened in severity during the conduct of a clinical study and does not necessarily have a causal relationship to study drug. Serious AEs (SAEs) included death, a life-threatening AE, inpatient hospitalization or prolongation of existing hospitalization, persistent or significant disability or, a congenital anomaly or birth defect, or an important medical event that jeopardized the participant and required medical intervention to prevent 1 of the outcomes listed in this definition. A TEAE was any AE with an onset on or after the day of infusion through Week 36 (end of study). AEs were graded per National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE): Grade: 1=Mild, 2=Moderate, 3=Severe or medically significant but not immediately life-threatening. A summary of serious and non-serious AEs regardless of causality is located in 'Reported Adverse Events module'.
| Participants | ANX005 |
|---|---|
| Any TEAEs | 28 |
| SAEs | 2 |
| AEs related to ANX005 | 28 |
| SAEs related to ANX005 | 2 |
| Grade ≥3 AEs | 12 |
| Grade ≥3 AEs related to ANX005 | 11 |
| AEs leading to study discontinuation | 2 |
| AEs leading to discontinuation of study medications | 4 |
| milligrams (mg)/kilogram (kg) | ANX005 |
|---|---|
| Actual Dose of ANX005 Administered on Day 1 | 75.0624 ± 2.6694 |
| mg/kg | ANX005 |
|---|---|
| Actual Dose of ANX005 Administered on Week 22 | 102.6609 ± 2.7408 |
| days*µg/milliliter (mL) | ANX005 |
|---|---|
| Area Under the Concentration Versus Time Curve From Time 0 to t (AUC0-t) of ANX005 at Day 1 | 4290 ± 818 |
| µg/mL | ANX005 |
|---|---|
| CSF Free Complement Component 1q (C1q) at Day 1 | 0.2297 ± 0.06239 |
| µg/mL | ANX005 |
|---|---|
| Blood Free C1q at Day 1 | 85.589 ± 14.0165 |
| µg/L | ANX005 |
|---|---|
| Change From Baseline in Complement C4a in CSF at Week 24 | 38.18 ± 14.423 |
| µg/L | ANX005 |
|---|---|
| Change From Baseline in Complement C4a in CSF at Week 36 | 23.28 ± 9.570 |
| ng/L | ANX005 |
|---|---|
| Change From Baseline in CSF NfL Level at Week 24 | 318.0 ± 618.66 |
| ng/L | ANX005 |
|---|---|
| Change From Baseline in CSF NfL Level at Week 36 | 508.6 ± 919.43 |
| ng/L | ANX005 |
|---|---|
| Change From Baseline in Blood NfL Level at Week 24 | -6.53 ± 10.112 |
| ng/L | ANX005 |
|---|---|
| Change From Baseline in Blood NfL Level at Week 36 | -2.20 ± 13.146 |
Collected over From first dose of study drug up to end of study (Week 36). Non-serious events are listed at a 5% frequency threshold.
| Group | Deaths | Serious | Other |
|---|---|---|---|
| ANX005 | 0/28 (0%) | 2/28 (7.1%) | 28/28 (100%) |
| Event | ANX005 |
|---|---|
| Systemic lupus erythematosusMusculoskeletal and connective tissue disorders | 1/28 |
| PneumonitisRespiratory, thoracic and mediastinal disorders | 1/28 |
| Event | ANX005 |
|---|---|
| RashSkin and subcutaneous tissue disorders | 15/28 |
| Rash maculo-papularSkin and subcutaneous tissue disorders | 10/28 |
| PruritusSkin and subcutaneous tissue disorders | 8/28 |
| DizzinessNervous system disorders | 6/28 |
| HeadacheNervous system disorders | 5/28 |
| NauseaGastrointestinal disorders | 5/28 |
| VomitingGastrointestinal disorders | 4/28 |
| COVID-19Infections and infestations | 4/28 |
| TachycardiaCardiac disorders | 4/28 |
| Rash macularSkin and subcutaneous tissue disorders | 3/28 |
Safety population included all enrolled participants who received at least 1 dose of study drug.
| Age, Continuous(years) | ANX005 |
|---|---|
| Mean | 49.7 ± 12.51 |
| Sex: Female, Male(Participants) | ANX005 |
|---|---|
| Female | 12 |
| Male | 16 |
| Ethnicity (NIH/OMB)(Participants) | ANX005 |
|---|---|
| Hispanic or Latino | 1 |
| Not Hispanic or Latino | 27 |
| Unknown or Not Reported | 0 |
| Race (NIH/OMB)(Participants) | ANX005 |
|---|---|
| American Indian or Alaska Native | 0 |
| Asian | 0 |
| Native Hawaiian or Other Pacific Islander | 0 |
| Black or African American | 0 |
| White | 28 |
| More than one race | 0 |
| Unknown or Not Reported | 0 |
| Complement C4a in Cerebrospinal Fluid (CSF)(micrograms (µg)/liter (L)) | ANX005 |
|---|---|
| Mean | 15.16 ± 6.092 |
| CSF Neurofilament Light Chain (NfL) Level(nanograms (ng)/L) | ANX005 |
|---|---|
| Mean | 3236.1 ± 816.74 |
| Blood NfL Level(ng/L) | ANX005 |
|---|---|
| Mean | 39.51 ± 11.661 |
| Blood C1q(µg/mL) | ANX005 |
|---|---|
| Mean | 85.589 ± 14.0165 |
1 further baseline measures are reported on the registry.
PDFs hosted by the registry, ClinicalTrials.gov.
Plan to share: No
Ran from Sep 2020 to primary completion in Aug 2022, 23 months.
Results were first posted in Aug 2026, 3 years 11 months after primary completion. A results delay was requested in Jan 2023.
Of 22 phase 2 interventional studies under Huntington Disease, half reached primary completion within 31 months of starting (the median), counting those still running; a quarter within 21 and three quarters within 40. This study's 23 months is below that.
How these figures are worked out, and which studies are left out of them.
This study is completed, as verified in Jul 2026. You cannot join it, but the record below documents what was studied.
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Studies of the drug tested here: Tanruprubart
Annexon, Inc.