Altohyrtin A (spongistatin 1, cinachyrolide A)[1] is a polyether macrolide originally isolated from the Okinawan marine sponge Hyrtios altum by Kobayashi et al. in 1993,[2] the Indian marine sponge Spongia sp.

by Pettit et al. in 1993,[3] and the Japanese marine sponge Cinachyra sp.

Altohyrtin A binds to the maytansine site on β-tubulin.

[5] While a producer organism for Altohyrtin A has never been isolated in pure culture, the structural features of Altohyrtin A, such as the 'odd-even' rule of methylation, and the abundance of oxygen heterocycles, suggest it is a product of dinoflagellate polyether metabolism.

[6] Alternatively, it may be a bacterial natural product.