PAH has not been described with asciminib, so it is important to consider other possible etiologies, including primary. Still, being a new drug, we must consider the possibility that there is some connection with the use (possibly related?). You could monitor closely and if it remains stable and asymptomatic continue therapy. Changing therapy is certainly reasonable if not improving and certainly if worsening. Of the TKIs, perhaps bosutinib or imatinib would be the safest in this setting. PAH has been described with dasatinib and ponatinib much more commonly (even when still a small percentage) with dasatinib and ponatinib so I would avoid these two. That would of course likely mean taking the patient off study but in such circumstances patients’ wellbeing should be considered first if you think asciminib is causing or at least contributing to this adverse event.
I hope this helps.