Is it possible to convert two annotations to a region?

We’re updating alert annotations via the Grafana API. I’d like to convert alerts to regions, but it doesn’t seem this is possible from what I’ve tried.

curl -vv -X PUT http://localhost:3001/api/annotations/103 -H "Content-Type: application/json" -H "Authorization: Bearer <token>==" -d '{"regionID":103}'

But when I query /api/annotations/ for 103, it still has "regionId": 0