Typical in vitro transcription (IVT) yields range from 2 to 8 mg/mL of mRNA. Conservative, non-optimized reactions typically produce 1-3 mg/mL, standard optimized conditions yield 3-5 mg/mL, and highly optimized reactions with co-transcriptional capping and optimized NTP/Mg2+ ratios can achieve 6-10 mg/mL. Yield depends on template quality, NTP concentration, T7 RNA polymerase concentration, magnesium levels, reaction temperature, and reaction duration. Longer mRNA transcripts (>4,000 nt) tend to have lower yields than shorter constructs.

A typical mRNA purification train includes: (1) DNase I digestion to remove the DNA template, followed by tangential flow filtration (TFF) for buffer exchange and concentration; (2) oligo-dT affinity chromatography to select for full-length, polyadenylated mRNA and remove truncated products; (3) ion exchange chromatography (IEX) to remove dsRNA impurities that cause innate immune activation; (4) TFF for final concentration and buffer exchange into formulation buffer; and (5) sterile filtration (0.2 um). Each step has an associated recovery yield, typically 80-97% per step, resulting in overall purification yields of 50-75%.

LNP encapsulation efficiency (EE%) measures the fraction of mRNA successfully incorporated into lipid nanoparticles during formulation. Modern microfluidic mixing methods achieve 85-95% EE, while older ethanol injection methods may achieve 60-80%. The N/P ratio (nitrogen-to-phosphate ratio) is a critical parameter controlling the ratio of ionizable lipid nitrogen groups to mRNA phosphate groups, typically optimized between 4 and 8. Higher N/P ratios generally improve EE but increase lipid use and may affect tolerability. EE directly impacts your final product yield and cost per dose.

The number of doses per batch depends on IVT scale, yield, purification recovery, LNP encapsulation efficiency, and dose size. For a COVID-19 vaccine at 30 ug/dose: a 1 mL IVT at 4 mg/mL yields approximately 90-120 doses after purification and LNP encapsulation. A 100 mL reaction produces approximately 9,000-12,000 doses, and a 1 L reaction can produce 90,000-120,000 doses. For higher-dose therapeutics (1-5 mg/dose), the same batch produces proportionally fewer doses. Manufacturing overfill (typically 15-20%) further reduces the number of deliverable doses.

The four major raw material cost drivers are: (1) NTPs (nucleoside triphosphates), which are consumed in large molar excess during IVT, costing $200-800/g depending on grade; (2) cap analogs such as CleanCap, which are extremely expensive at $5,000-25,000/g for GMP-grade material; (3) T7 RNA polymerase at $50-200/mg; and (4) lipids for LNP formulation, including ionizable lipid, DSPC, cholesterol, and PEG-lipid, collectively costing $1,500-8,000/g at GMP grade. At research scale, NTPs and cap analogs dominate costs. At GMP manufacturing scale, lipid costs often become the largest contributor, particularly for proprietary ionizable lipids.

IVT scale-up follows relatively linear economics since the reaction is cell-free and occurs in simple stirred reactors. Moving from 1 mL to 1 L increases output approximately 1000-fold with similar per-mL yields if mixing and temperature control are maintained. Beyond 1 L, large-scale IVT reactions (5-50 L) are used for commercial manufacturing. The primary challenges at scale are ensuring uniform mixing of the viscous reaction mixture, maintaining consistent temperature, and scaling the downstream purification train proportionally. Cost per dose typically decreases with scale due to fixed costs being distributed across more doses, but raw material costs per mg remain relatively constant.