[OT] how to change the first character into upper case

[lina <lina.lastname@gmail.com>]

Sorry a bit off-topic, but I am stuck with how to tr
(googled some ways out, still not work)

NELSON ARISPE, EDUARDO ROJAS, AND HARVEY B. POLLARD

into

Nelson Arispe, Eduardo Rojas, and Harvey B. Pollard

Here is what I came up with so far:

 echo "NELSON ARISPE, EDUARDO ROJAS, AND HARVEY B. POLLARD" | sed
's/\([A-Z]\)\([A-Z]+\)/\1\L\2/g'

not work.

Thanks with best regards,