The polyunsaturated fatty acid (PUFA) ω-3 cis-7,10,13,16,19-docosapentaenoic acid (DPAn-3) is an intermediate in the biosynthesis of docosahexaenoic acid (DHA) from eicosapentaenoic acid (EPA) and is also a precursor for the production of novel bioactive mediators.The proposed biosynthesis of maresins derived from DPAn-3 is described here (Dalli et al. 2013, Hansen et al. 2017, Vik et al. 2017). 12-lipoxygenase oxygenates DPAn-3 to its 14(S) hydroperoxy epimer from which maresins are formed via a combination of oxygenation, reduction and hydrolysis reactions (Dalli et al. 2013). The products of the ω-3 isomer were characterised based on docosahexaenoic acid (DHA)-derived maresins (Serhan et al. 2015) and were demonstrated to have similar potent systemic anti-inflammatory and tissue protective actions as DHA-derived specialised proresolving mediators (SPMs) (Dalli et al. 2013). The same biosynthetic route as DHA-derived SPMs is probably how DPAn-3 products are also formed (Dalli et al. 2013).