VScode - regex find match in the middle and remove start and end

Question

I want to replace all (start and end) of the string but the parameter in the middle (for example @ModelKey or @ProductNumber) from this Input

[MODEL_KEY] = IIF(@ModelKey IS NOT NULL, @ModelKey , [MODEL_KEY]), 
[PRODUCT_NUMBER] = IIF(@ProductNumber IS NOT NULL, @ProductNumber , [PRODUCT_NUMBER]), 

i need this output

@ModelKey
@ProductNumber

In my regex101.com example this works

(.*)(\@.*)(\sIS)(.*)

as expected

1. Group $1 (.*) for example [MODEL_KEY] = IIF( can be removed
2. Group $2 (\@.*) is the group to keep @ModelKey
3. Group $3 and $4 (\sIS)(.*) are the groups that can be removed

As you can see in this image

But in vs code the expression (.*)(\@.*)(\sIS)(.*) results in an error message:

Invalid regular expression

Invalid esape

Question

• Does visual-studio-code uses the same regex syntax as ecmascript?
• What must be changed to make the regex work in vs-code?