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.