English to Hebrew Medical Medical (general) transcription question

I was asked regarding translation of the name of a new experimental drug Tocilizumab. The agency received 2 different spelling: טוסיליזומאב or טוציליזומאב. I voted for the later, as ci and ce usually transcribed with צ, right? like in various antibiotics etc. However, when I googled it, I received 134 votes for the use of 'ס' and only 2 votes for the use of 'צ'.
What do you think? Are there any rules about it?
Many thanks in advance!