To cite an article from the 1998 AAPS PharmSci Supplement:

Authors Title Journal Supplement. Year; Volume (Issue) Available from: URL.

For example:

A.E. Radwick and D.J. Burgess MECHANISM OF FORMATION OF A NOVEL SELF- ASSEMBLED MICROSPHERE SYSTEM AAPS PharmSci 1998 AAPS Annual Meeting Supplement. 1999; 1 (1) Available from: https://www.aapspharmaceutica.com/scientificjournals/pharmsci/am_abstracts/1998/abstracts/2303.html.

This follows the American Medical Association standard format for online journals.