Hello Alan,
First off I do understand very well MS and your situation, my mother suffers from MS for the past 24 years, when she was diagnosed she underwent therapy with Interferon Beta 1-a.
I did research your question and could not find the answer you need, but did find the following:
"The average half-life of ocrelizumab in the body is approximately 28 days. Following administration, B-cells are rapidly depleted and can remain undetectable for a prolonged and variable period of time ranging from 6 months to more than 12 months."
Source: Cleveland Clinic Mellen Center for Multiple Sclerosis
Be strong, don't stop fighting and never lose your faith, work with a Neurologist that is committed on treating you not just as one more patient, that was crucial for my mother.
The Interferon Beta 1-a helped my mother (as you know everyone reacts differently to medications) by stopping the immune system from progressing and attacking the healthy cells, cells in the myelin, as you know.
All the best, masso