EA-3148 (Substance 100A) is a "V-series" nerve agent related to the better-known compounds VX and VR.

[1] It was studied by both the US and Soviet chemical weapons programmes during the Cold War, and is notable as the only V-series organophosphate nerve agent specifically identified in public domain sources as having a higher absolute potency as an acetylcholinesterase inhibitor than VX (around 50% more potent by weight).

[2] However, both the US and Soviet investigations of the compound concluded that despite its high potency, the physicochemical properties of the substance made it unsuitable for weaponisation, and further research was not conducted.

Signs of toxicity were evident within 5-8 min of treatment in two comparably dosed subjects who felt dizzy, weak, tired, sweaty, and had hands and feet that were moist.

A U.S. Army report summarizing experience with EA-3148 noted anorexia, fatigue, poor sleep, unusual dreams, dizziness, euphoria, blurred vision, increased salivation, restlessness; decrements in a test of numerical facility in four individuals and exaggeration of a schizoid personality in one male soldier.