**Michael T. Davies-Coleman 1,\* and Clinton G. L. Veale <sup>2</sup>**


Academic Editor: Sylvia Urban Received: 25 July 2015; Accepted: 29 September 2015; Published: 14 October 2015

**Abstract:** Recent developments in marine drug discovery from three South African marine invertebrates, the tube worm *Cephalodiscus gilchristi*, the ascidian *Lissoclinum* sp. and the sponge *Topsentia pachastrelloides*, are presented. Recent reports of the bioactivity and synthesis of the anti-cancer secondary metabolites cephalostatin and mandelalides (from *C. gilchristi* and *Lissoclinum* sp., respectively) and various analogues are presented. The threat of drug-resistant pathogens, e.g., methicillin-resistant *Staphylococcus aureus* (MRSA), is assuming greater global significance, and medicinal chemistry strategies to exploit the potent MRSA PK inhibition, first revealed by two marine secondary metabolites, *cis*-3,4-dihydrohamacanthin B and bromodeoxytopsentin from *T. pachastrelloides*, are compared.

**Keywords:** cephalostatin; mandelalide; methicillin resistant *Staphylococcus aureus*; MRSA PK; bisindole alkaloids
