How to Make a Mechanism-of-Action (MOA) Figure

Mechanism-of-action (MOA) figures explain how a drug or molecule produces its effect — the binding event, the downstream pathway, the cellular outcome. They're heavily reused in reviews, talks, and teaching, so a clear one extends your work's reach. The challenge is showing a multi-step process without overwhelming the reader.

1. Define the start and end points

Every MOA figure tells a journey: from the drug/ligand arriving to the final physiological outcome. Pin down those two anchors first, then map the essential steps between them. Omit detail that doesn't change the take-home message.

2. Establish a spatial frame

Most MOA figures use a cell or tissue as the stage — extracellular space, membrane, cytoplasm, nucleus. Lay this out clearly so each event sits in its correct compartment. A believable membrane and organelles help; see our cell modelling guide if you want 3D.

3. Show the target interaction clearly

The binding event (drug to receptor/enzyme) is the heart of the figure. Make it visually prominent — often a zoom-in or inset. If structure matters, a rendered molecule (via ChimeraX to Blender) adds authority.

4. Use numbered steps and consistent arrows

• Number the steps (1, 2, 3) so readers follow the sequence.
• Use one arrow style for activation and a clearly different one for inhibition (a blunt-ended line is the convention for inhibition).
• Keep arrow directions consistent with the flow of causality.

5. Colour-code meaningfully

Assign colour to function — for example, one colour for the drug, one for the pathway it activates, one for what it blocks — and add a small legend. Keep it colourblind-safe (palette guide) and limited to a few hues.

6. Label precisely, abbreviate carefully

Use correct gene/protein nomenclature, define abbreviations in the caption, and place labels right next to the elements they name. A clean sans-serif keeps it readable (font guide).

7. Keep it honest

Distinguish established mechanism from proposed or hypothetical steps — a dashed arrow or a "?" is the honest way to flag uncertainty. Overstating a mechanism your data don't fully support is a credibility risk and a reviewer red flag.

8. Build it in the right tool

2D vector tools (Inkscape, Illustrator) are ideal for schematic MOA figures; Blender adds depth when a 3D membrane or molecule strengthens the story. Match the tool to how much realism the message needs.