Appendix: Chemical structures
The first on the left is spongothymidine, the first sponge nucleoside isolated. Next to it is ara C, or spongocytidine, or cytarabine, or the trade name Cytosar (TM).
For comparison, below are the building blocks of DNA, the deoxynucleosides: A, G, C, T:
The new ALL treatment, ara G:
Below is clofarabine, and then the drugs that inspired it, cladribine and fludarabine:
Acyclovir is an antiviral, AZT is anti-HIV, and gemticibine is anti-cancer. They are all nucleoside analogues.