Engineering RNA stability has become a cornerstone of modern therapeutics, almost entirely in one direction: mRNA vaccines established stabilisation of exogenous transcripts as a powerful design axis. The symmetric operation-exploitation of instability in endogenous targets-has been comparatively underexplored. We argue that target RNA half-life is an underused but quantitatively consequential design parameter for antisense oligonucleotide (ASO) therapeutics, and that short-lived long noncoding RNAs (lncRNAs) are a particularly attractive target class. Under sustained ASO dosing, the time to a new steady state is set by the sum of the target's own decay rate and the ASO-induced decay rate, so-for a given depth of knockdown-endogenous half-life becomes a major determinant of pharmacodynamic onset alongside ASO potency and delivery, most directly for RNase H-dependent gapmers; we treat the resulting first-order relationships as a qualitative design heuristic rather than a quantitative pharmacokinetic/pharmacodynamic model. Two back-to-back 2012 surveys-BRIC-seq in human HeLa and actinomycin-D microarray in mouse Neuro-2a-yielded similar median lncRNA half-lives of 3.4 and 3.5 h, with a short-lived fraction we term short-lived noncoding transcripts (SLiTs; t1/2 < 4 h). SLiTs include several disease-relevant regulators (GAS5, NEAT1, CDKN2B-AS1/ANRIL, HOTAIR, TUG1); their rapid turnover supports fast onset, reversibility and tight titratability. We (i) develop a kinetic framework for how target half-life shapes ASO pharmacodynamic onset, (ii) survey the cross-species half-life landscape, (iii) propose a decay-pathway-aware ASO design framework aligning modality choice with endogenous decay machinery, (iv) re-read representative clinical ASO cases (nusinersen, tofersen, tominersen, MALAT1 ASOs) through the half-life lens, and (v) outline a half-life-aware preclinical roadmap. Treating half-life symmetrically-engineered up in vaccine RNAs, exploited downward in endogenous targets-highlights a largely unoccupied design space for next-generation oligonucleotide therapeutics.
