Conventional mRNA therapeutics are commonly manufactured in two stages: a DNA template is first amplified and prepared, followed by an in vitro transcription reaction that converts this template into the final mRNA product. DNA template production can be slow, error‑prone and introduce contaminants, motivating the development of fully cell‑free mRNA manufacturing strategies. The Bicycle reaction is an approach that merges in vitro transcription and reverse transcription into a single circular process, enabling exponential mRNA amplification directly from basic starting materials. This reaction generates high‑quality mRNAs with defined sequence fidelity, structural integrity and purity, supporting efficient cellular translation with low reactogenicity. The Bicycle reaction can produce a broad spectrum of mRNA therapeutics spanning different lengths and applications. By compressing mRNA synthesis into one isothermal, single‑pot enzymatic step, the Bicycle reaction streamlines production and reduces the time, cost and complexity associated with making mRNA medicines.