NSEO on my website

Hi everyone.
One of my websites is actualy under an Negative SEO campaign.
Since the 1st december I got nearly 10K backlinks with "Viagra" as anchor text.
Now i have the same number of backlinks with viagra than with my main KW.

I can't use the disavow link beacause there are realy too much links every days...
What can i do to prevent that ?

Thanks all.