On-demand pharmaceuticals in space: Bacillus subtilis revolutionizes astropharmacy

Producing critical medications like biologics in space paves the way for sustainable human exploration beyond Earth

As humanity reaches for the stars, a challenge stands out: ensuring a reliable supply of medications for long-duration flights to Mars and beyond. Astronauts will get sick hundreds of thousands of miles away from the nearest pharmacy. How do we produce life-saving medicines in the vastness of space? The answer: Bacillus subtilis engineered to produce pharmaceuticals on demand.

In preparation for long-duration space missions, where resupply from Earth isn’t an option, the concept of an astropharmacy emerges. Imagine a platform for a low-mass, on-demand drug production system in space. Here, therapeutic doses of any protein-based biopharmaceutical will be manufactured according to instructions written in strands of an organism’s DNA. Want a different drug? Use a different DNA sequence!

A fully operational astropharmacy, as envisioned by Vallota-Eastman et al. (2023), will encompass four components: drug synthesis, purification, testing, and administration. In this publication, the authors discuss the first step: drug synthesis using B. subtilis, the space-hardy "microbial astronaut."

Why B. subtilis?

B. subtilis is known for its incredible resilience in space with its endospores surviving the vacuum of space for nearly 6 years on NASA’s long-duration mission. Besides being able to withstand harsh conditions, B. subtilis has long been used for expressing therapeutic proteins to treat conditions ranging from diabetes to cystic fibrosis. In this proof-of-concept study, researchers engineered B. subtilis strains to produce two key peptides that would be essential for astronaut health during long-duration space missions: teriparatide, which combats bone loss, and filgrastim, which counters radiation-induced blood cell damage.

Producing biologics in space

Teriparatide or recombinant human parathyroid hormone is an FDA-approved biologic that increases bone mineralization and would be crucial for maintaining bone density in microgravity. Teriparatide was fused to a library of secretion peptides and the best-performing construct was inserted into the genome of B. subtilis. Researchers engineered B. subtilis to secrete teriparatide using a fusion construct. The result? A single dose of teriparatide could be produced in just 24 hours from a mere 2 ml of culture. This innovation could ensure that astronauts maintain bone health on extended missions without relying on Earth-bound supplies.

Filgrastim or human recombinant granulocyte colony stimulating factor is FDA approved to treat low-neutrophil blood count. Radiation exposure remains one of the most pressing issues in astrophysiology and filgrastim can support the hematopoietic system by helping restore neutrophil counts in the event of acute radiation exposure. Producing filgrastim in B. subtilis from a fusion construct was challenging, with a production rate that was twofold lower and a dose requirement that is tenfold greater than that of teriparatide. The lower secretion rate was possibly due to filgrastim being cytotoxic to B. subtilis cells. The cytotoxicity was partly alleviated when filgrastim was expressed at a lower concentration, and a dose equivalent of filgrastim could be produced from 52 ml of culture within 24 hours.

The engineering of B.subtilis to produce teriparatide and filgrastim represents a major leap forward in space medicine, a proof of concept towards realizing the vision of an astropharmacy—ensuring astronauts have the medicines they need, when they need them.

Looking ahead, further optimization of strain growth conditions, expression systems, and promoter sequences is needed to increase production efficiency. The problem of pharmaceutical toxicity to cells is not uncommon, and not all protein-based pharmaceuticals will be amenable to recombinant expression in every strain. Consequently, significant cloning efforts and the testing of various host cells will be necessary for each new pharmaceutical needed.

References

Vallota-Eastman, A. et al. Bacillus subtilis engineered for aerospace medicine: a platform for on-demand production of pharmaceutical peptides. Front. Space Technol., Sec. Space Exploration 4 (2023).

Takara Bio products used in this exciting study

PrimeSTAR® Max DNA Polymerase 
In-Fusion® Snap Assembly Master Mix
Stellar™ Competent Cells
B. Subtilis Secretory Protein Expression System
NucleoSpin® Gel and PCR Clean-Up kit