Messenger RNA (mRNA)–lipid nanoparticle (LNP) technologies have become central to the development of next-generation vaccines and therapeutics. As these platforms advance from early discovery to clinical application, an integrated, phase-appropriate development strategy is essential for ensuring both scientific rigor and regulatory alignment. This review provides a comprehensive framework to guide translational research teams through the complex landscape of mRNA–LNP product development, from initial design decisions to first-in-human trials. We examine key considerations in mRNA construct optimization, lipid nanoparticle formulation, and analytical characterization, emphasizing the importance of early analytical method development for identity, purity, potency, and stability. Nonclinical strategies, including proof-of-concept pharmacology, biodistribution, and toxicology, are discussed with a focus on distinguishing between vaccine and therapeutic applications. Clinical development considerations are also explored, highlighting dose escalation, safety monitoring, and immune profiling. This phase-appropriate approach aims to assist fundamental research teams in bridging the gap from preclinical discoveries to IND-enabling clinical trials. With a background in early drug development across various therapeutic areas, the author has been involved in regulatory submissions, scientific and business assessments, and the development of complex delivery systems, including liposomal and nanoparticulate formulations. Drawing on this experience, the author aims to contribute to the ongoing dialogue between fundamental researchers and the clinical development process, helping to translate promising innovations into tangible patient outcomes.