400 mg sertraline is a very typical move for me. The OCD expert I trained with tended to very aggressively up-titrate people from 200 to 400 mg after a trial of 200 (like, over the space of two weeks). He felt there was unlikely to be improvement in the middle of this range and so it was best to get to the maximally effective dose as quickly as possible. Perhaps consistent with
@mistafab I have seen more of my patients get some benefit from 300 mg (often because we had to slow down the titration for a prolonged period of time due to side effects) so I am increasingly actually trying 300 deliberately before moving to 400 more often.
I continue to be unimpressed by memantine, I can think of only 2-3 cases where I am convinced it did anything positive.
Re:clomipramine, it is often enough clearly superior to the response to SSRIs that if there is data failing to show superiority, so much worse for the data. Sometimes even relatively small (~50 mg) doses of it produce surprising gains, especially when it serves to "unstick" patients who have plateau'd in E/RP. More than one person I work with sing the praises of clomipramine and want to stay on it at all costs while also experiencing fairly strong versions of the expected side effects that do genuinely bother them. That said, my clomipramine success stories tend to be closer to the 250 end of the OCD dosing range.
Neuroleptic-induced obsessive compulsive symptoms are indeed a thing, incidence appears to be related to how similar the antipsychotic in question is to clozapine (so clozapine #1, olanzapine much lower #2, everything else a distant #3). It will be interesting to see if this is observable when we have better long-term data about Cobenfy.
The MAO-I that has specific evidence for OCD is phenelzine. Definitely an option but a hard sell, many people with OCD get extremely nervous when you start talking about potentially lethal side effects. And I say this as someone who uses MAOIs significantly more than I think the average psychiatrist.