According to chemical weapons expert Jonathan Tucker, the first binary formulation developed under the Soviet Foliant program was used to make Substance 33, differing from VX only in the alkyl substituents on its nitrogen and oxygen atoms.

According to UK Defence Science and Technology Laboratory Detection Department scientists Robin M. Black and John M. Harrison, chemical stability was an important factor why of all the similarly toxic phosphorylthiocholines, ethyl N-2-diisopropylaminoethyl methylphosphonothiolate in particular (now known as VX), was weaponized in the West.

[10] According to Russian CW developer Vil Mirzayanov, in the late 1980s a group of GosNIIOKhT chemists led by Georgiy Drozd prepared a scientific report that Substance 33 had much lower shelf life than VX.

[11] Following the poisoning of Sergei and Yulia Skripal, former head of the GosNIIOKhT security department Nikolay Volodin said in an interview to Novaya Gazeta that Substance 33 was decomposing too quickly in combat conditions, and implied that this fact may have influenced the decision to continue research on the Novichok program.

However, the window for effectively treating second generation V series seizures is shorter, as they rapidly denature the acetylcholinesterase protein in a similar manner to soman, making treatment with the standard nerve gas antidote pralidoxime ineffective unless it is given very soon after exposure.