C1QA

Complement C1q A Chain

Score: 0.546 Price: $0.55 Low Druggability Status: active Wiki: C1QA

🧠 Neurodegeneration

HYPOTHESES

5

PAPERS

44

KG EDGES

193

DEBATES

1

3D Protein Structure

🧬 C1QA — PDB 1PK6 Click to expand

Experimental structure from RCSB PDB | Powered by Mol*

Druggability & Clinical Context

Druggability

Low

Score: 0.41

Clinical Stage

Phase II

Target Class

Signaling Protein

Safety

0.45

Druggability Analysis

Drug Development0.35

Structural Tractability0.70

Target Class0.50

Safety Profile0.45

Key Metrics

PDB Structures:

4

Known Drugs:

1

Approved:

0

In Clinical Trials:

1

Drug Pipeline (1 compounds)

1 Phase II

Druggability Rationale: C1QA demonstrates medium druggability (0.55) supported by strong structural data (4 PDB structures at 1.25 Å resolution, AlphaFold and cryo-EM availability) and clinical validation via ANX005 in Phase 2 trials. However, as a secreted signaling protein component of the C1 complex, it is inherently challenging to drug with small molecules, favoring antibody-based or protein-based therapeutic modalities over traditional ligand approaches.

Mechanism: Complement cascade inhibitor or antibody-mediated neutralization

Drug Pipeline (1 compounds)

1 Phase II

Known Drugs:

ANX005 (phase_2) — complement-mediated diseases

Structural Data:

PDB (4) ✓AlphaFold ✓Cryo-EM ✓

5HBA 5HKJ 5HZF 6Z6V

UniProt: A0A8Q3SI59

🧬 3D Protein Structure

🧬 C1QA — PDB 1PK6 Click to expand interactive 3D viewer

Experimental structure from RCSB PDB | Powered by Mol* | Rotate: click+drag | Zoom: scroll

Selectivity & Safety Considerations

C1QA selectivity is primarily a concern at the pathway level rather than isoform level, as antibody-mediated approaches (like ANX005) must distinguish between C1q and related complement components (C1r, C1s) to avoid unintended pathway inhibition. Off-target risks include broader complement system suppression affecting immune homeostasis and infection susceptibility.

3D Protein Structure

PDB: Open in RCSB AlphaFold model

Interactive 3D viewer powered by RCSB PDB / Mol*. Use mouse to rotate, scroll to zoom.

Clinical Trials (7)

Relevant trials from ClinicalTrials.gov

Active

1

Completed

5

Total Enrollment

364

By Phase

PHASE1: 2 · PHASE2: 3 · PHASE3: 2

An Open Label Clinical Study to Evaluate Tanruprubart (Also Commonly Known as ANX005) in Participants With Guillain-Barr Recruiting

PHASE3 NCT07020819 n=30

Guillain-Barre Syndrome

Interventions: Tanruprubart

Sponsor: Annexon, Inc. | Started: 2025-09-12

Efficacy and Safety of ANX005 in Subjects With Guillain-Barré Syndrome Completed

PHASE3 NCT04701164 n=242

Guillain-Barre Syndrome

Interventions: ANX005, Placebo

Sponsor: Annexon, Inc. | Started: 2020-12-17

Study of ANX005 in Adults With Amyotrophic Lateral Sclerosis (ALS) Completed

PHASE2 NCT04569435 n=17

Amyotrophic Lateral Sclerosis

Interventions: ANX005

Sponsor: Annexon, Inc. | Started: 2021-01-15

An Open Label Study of ANX005 in Subjects With, or at Risk for, Manifest Huntington's Disease Completed

PHASE2 NCT04514367 n=28

Huntington Disease

Interventions: ANX005

Sponsor: Annexon, Inc. | Started: 2020-08-17

Safety, Tolerability, Pharmacokinetics and Pharmacodynamics of ANX005 in Participants With Warm Autoimmune Hemolytic Ane Completed

PHASE2 NCT04691570 n=6

Warm Autoimmune Hemolytic Anemia (wAIHA)

Interventions: ANX005

Sponsor: Annexon, Inc. | Started: 2021-11-10

A Clinical Study of ANX005 and IVIG in Subjects With Guillain Barré Syndrome (GBS) Completed

PHASE1 NCT04035135 n=14

Guillain-Barré Syndrome

Interventions: ANX005, Intravenous immunoglobulin

Sponsor: Annexon, Inc. | Started: 2020-01-29

Single Dose Study of ANX005 in Healthy Volunteers Terminated

PHASE1 NCT03010046 n=27

Safety and Tolerability in Healthy Volun

Interventions: ANX005, IVIg, Placebos

Sponsor: Annexon, Inc. | Started: 2016-12

Linked Hypotheses (6)

Complement C1q Mimetic Decoy Therapy0.695

Complement C1QA Spatial Gradient in Cortical Layers0.678

Complement C1q Subtype Switching0.665

Complement-Mediated Synaptic Pruning Dysregulation0.612

Complement-Mediated Synaptic Protection0.580

Complement C1q Suppression as Mechanism Linking Exercise Plasma to PV Interneuron Protection0.560

Linked Experiments (0)

No linked experiments

Scoring Dimensions

Knowledge Graph (20)

activates (5)

CTSB→C1QAC1QA→SPP1C1QA→GRNC1Q→C1QAC1QA→C1QC

associated with (2)

C1QA→neurodegenerationGBM→C1QA

co discussed (13)

NTN1→C1QAHSPG2→C1QAP2RY12→C1QAP2RX7→C1QAAQP4→C1QA

▸ Show 8 more

EPHB4→C1QASMPD1→C1QAC1QA→CERS2HK2→C1QATREM2→C1QAC1Q→C1QAC1QA→CX3CR1C1QA→ANXA1

Debate History (1)

Should C1QA (Complement C1q A Chain) be prioritized as a therapeutic target for 2026-04-22