Short story is that these 'Novichoks' are real compounds studied in the USSR at bench scale in the 1970s, at a time when several countries were studying possible new nerve agents.
The story of a secret programme in the late 80s / early 90s to develop a chemical super-weapon named "Novichok" was fabricated by Soviet counter-intelligence to successfully flush Vil Sultanovich Mirzayanov out as a US spy/leaker, and continued after the collapse of the USSR to confuse the US.
https://consortiumnews.com/2018/04/17/an-alternative-explantion-to-the -skripal-mystery/
The authentic looking secret material which he was deliberately given access to as a test of his loyalty did indeed 'find its way' to United States intelligence.
He was arrested in 1992 but the trial collapsed under Yeltsin and he moved to live in the United States in 1995.
The US studied the toxicity of these compounds around 1996, and all indications were they are not as toxic as Sarin or VX.
Their structures have been publicly available since 2008, so anyone with a reasonable lab can make them at bench scale.
