Fed-batch in vitro transcription process
The present disclosure provides methods of in vitro transcribing a ribonucleic acid (RNA) of interest. In some embodiments, such methods include determining consumption rates of nucleoside triphosphates (NTPs).
1. A method of fed-batch in vitro transcription (IVT) of a messenger ribonucleic acid (mRNA) of interest comprising:
(a) conducting an IVT reaction with an initial reaction mixture that comprises (i) deoxyribonucleic acid (DNA) encoding an mRNA of interest, (ii) an RNA polymerase, (iii) an initial concentration of nucleoside triphosphates (NTPs) comprising adenosine triphosphate (ATP), cytidine triphosphate (CTP), uridine triphosphate (UTP), and guanosine triphosphate (GTP), and (iv) an RNA cap analog; and
(b) delivering a feed stock mixture at a continuous flow rate to an ongoing IVT reaction mixture that comprises the initial reaction mixture, wherein the feedstock
(i) comprises NTPs comprising ATP, CTP, UTP, and GTP at a molar ratio based on percent consumption values that are specific to the mRNA of interest and are calculated separately for each of the NTPs,
wherein the percent consumption values are determined using an initial nucleotide empirical balancing reaction, and
(ii) is delivered in an amount that maintains a total concentration of NTPs in the ongoing reaction mixture that is at least between 5% to 50% of the initial concentration NTPs, thereby producing a transcribed mRNA of interest.
2. The method of claim 1 , wherein the continuous flow rate is 2-8 mL/min.
3. The method of claim 1 , wherein the initial reaction mixture of (a) comprises a ratio of [ATP]:[UTP] of 1:1 to 4:1 and/or a ratio of [GTP]:[CTP] of 1:1 to 4:1.
4. The method of claim 1 , wherein each of the NTPs in the initial reaction mixture of (a) is present at a concentration of 1-10 mM.
5. The method of claim 1 , wherein at least 90% of the transcribed mRNA of interest comprises the cap analog.
6. The method of claim 1 , wherein at least 95% of the transcribed mRNA of interest comprises the cap analog.
7. The method of claim 1 , wherein the ongoing IVT reaction mixture comprises an RNA cap analog to ATP ratio of greater than 0.6 and/or an RNA cap analog to GTP ratio of greater than 0.6.
8. The method of claim 1 , wherein the transcribed mRNA of interest comprises a length of longer than 100 nucleotides.
9. The method of claim 1 , wherein the initial IVT reaction mixture and the ongoing IVT reaction mixture further comprise a buffer.
10. The method of claim 1 , wherein the initial IVT reaction mixture and the ongoing IVT reaction mixture further comprise magnesium.
11. The method of claim 1 , wherein the feedstock mixture does not include DNA encoding the mRNA of interest or the RNA cap analog.
12. The method of claim 1 , wherein each NTP in the initial reaction mixture of (a) is present in an equimolar concentration for each NTP.
13. The method of claim 1 , wherein at least one of the ATP, CTP, UTP, and/or GTP molecules is a modified ATP, CTP, UTP, and/or GTP molecule.
14. The method of claim 1 , wherein the RNA cap analog is a chemically modified RNA cap analog, a naturally-occurring RNA cap analog, or a synthetic RNA cap analog.
15. The method of claim 1 , wherein the initial and ongoing IVT reaction mixtures comprise a ratio of [RNA cap analog]:[purine] of 1:1 to 20:1, 1:1 to 15:1, 1:1 to 10:1, 1:1 to 5:1, 1:1 to 3:1, or 1:1 to 2:1.
16. The method of claim 1 , wherein the ongoing IVT reaction mixture is not supplemented with an RNA cap analog during the IVT reaction.
17. The method of claim 1 , wherein the DNA concentration in the initial reaction mixture is 0.025-0.075 mg/mL.
18. The method of claim 1 , wherein the RNA cap analog is a dinucleotide cap, a trinucleotide cap, or a tetranucleotide cap.
19. The method of claim 1 , wherein the UTP is a 1-methylpseudouridine.