APA format allows for many ways to reference a variety of online sources including items on online forums or other postings.
The webpage is:
www.owl.english.purdue.edu/owl/resource/560/10.
Apparently, erlotinib is lipophilic. There was one article I found in the literature discussing this point in the treatment of a 12 year old girl with cystic fibrosis who also had a high grade glioma.
The article abstract link is:
www.ncbi.nlm.nih.gov/pmc/articles/PMC2704987.