Protein crystallization for drug formulation

Who it is for

• Biologics formulation teams developing high-concentration antibody suspensions for injection under the skin
• Structural biology and drug-discovery labs that need higher-resolution crystal structures of target proteins
• Contract research organizations that offer crystallization screening
• Academic crystallography groups testing how convection affects crystal quality
• Small-molecule polymorph screening, but only for solution processes that work between 4 and 45 C

What earlier flights found

How LELP-1 runs it

Sample. A purified, highly homogeneous target protein (for example a monoclonal antibody at 20-40 mg/ml, or a protein for X-ray structure work) with a viscous precipitant such as PEG. The conditions are fixed in ground tests before flight. Container. Large-bay 24-well cassette. 16 sealed batch wells (about 0.5-1 ml each), with protein and precipitant kept in separate reservoirs until the fluidics mix them in orbit. 8 positions hold gel-plugged counter-diffusion capillaries (JAXA style), with the precipitant added by the fluidics at activation. Launch. Live protein solution and precipitant in separate reservoirs, held at 4 C. No crystallization before activation. Not cryopreserved, because freezing would ruin the experiment. Light and gas. No light needed except for brief microscope imaging. No gas exchange: sealed wells, no CO2 or O2 supply.

1. day -1

   Late load of the filled cassette at 4 C into the powered bay on the pad. A matching ground-control cassette from the same protein lot is loaded at the same time.

2. day 0

   Launch. Bay holds 4 C. Accelerometer and dosimeter logging start.

3. day 1

   Arm parked and quiet microgravity confirmed (about 1e-6 g). Baseline brightfield images of all wells. Fluidics mix protein and precipitant in the batch wells and fill the counter-diffusion reservoirs (activation).

4. day 1

   Temperature step or ramp to the customer's growth setpoint. Default is 20 C, as in JAXA's PCRF. A warming ramp like Merck's (4 C to 30 C) is also possible, with the ramp rate set by the customer.

5. day 2

   Automated brightfield imaging of chosen wells every 6 h to record nucleation time, crystal count and size. Optional fluorescence if the customer adds a trace-labelled protein.

6. day 5

   Mid-point check of images on the ground. The customer may change the temperature profile of later wells with a signed command.

7. day 9

   Last full imaging pass. Bay set to the customer's return hold temperature. No fixative is added, because crystals stay in their mother liquor.

8. day 10

   End of lab operations. Deorbit, reentry and splashdown with the bay still under thermal control. Cassette handed to the courier about 20 min after splashdown in an active thermal shipper at the same setpoint.

The payload module, in CAD

Every item in the module sheet, drawn and packed into the large bay deck by deck. The back face mates with the bay: blind-mate connector, and a cold wall against the bay's thermoelectric block. The front face carries Dexter-L's grapple fixture, and the fluid lines run down a channel just behind it. What you load before launch is marked blue in the configurator's payload guide.

CAD generated by cad/build_modules.py (CadQuery, OpenCascade kernel) from the catalog's module items: concept geometry, not a released design. Standard parts keep their real formats; the rest are sized from their catalog mass. The front panel and grapple fixture are left off in the 3-D view and are in the STEP.

• The XY stage travels 96.5 x 57.9 mm, so every one of the 24 wells reaches the objective; with the stage the imaging stack is 232 x 151 mm, which sets the module's depth budget.
• Reagent volumes the catalog does not state are split evenly from 75 % of the reservoir item's mass.
• Fluid pack: 2 reagent bags in 1 layer (189 x 139 x 23 mm), every port on a front edge.
• The catalog gives 0.60 kg for structure and containment; as an aluminium box that is a 0.30 mm skin on 0.18 kg of posts and shelves. Thin: the bay rails have to carry the launch loads, or the module needs more structure mass.
• The grapple fixture stands 26 mm proud of the front panel, into the bay opening; everything else is inside the bay envelope.

Ground control

A matching cassette from the same protein lot and solutions, loaded at the same time, runs in a flight-equivalent bay on the ground. Telemetry drives its temperature to replay the flight log, including launch, activation, ramp and return-hold phases. It is activated at the same time by the same type of fluidics. Ideally a launch-vibration profile is applied before activation. Ground and flight samples go to the same lab and are analysed blind with the same methods. A third passive set, never activated, can show what launch and return alone do to the solutions.

Coming home

Hold the cassette at the customer's growth or hold temperature (default 20 C, within about +/-2 C) from end of growth to the lab. Do not warm, cool or freeze it unless ground tests show that is safe for that protein. How crystals react to temperature depends on the protein: pembrolizumab crystallized on warming from 4 to 30 C, while JAXA saw space-grown crystals degrade when Soyuz rose above 30 C on return. Handle gently, because crystals sit in liquid and can break under shock. The 72 h limit is our estimate (about 20 min to courier handover plus 1-2 days to the lab) and must be confirmed in ground tests for each protein.

Limits of this flight

• Lab operations last at most 14 days. Merck's samples spent 18 days in the incubator and JAXA growth took six weeks to four months, so LELP-1 suits only fast-growing systems whose conditions are fixed on the ground beforehand.
• There is no crew to harvest, mount or flash-cool crystals in orbit. Crystals come back in their mother liquor and can be damaged by reentry and splashdown shocks or by temperature excursions.
• There is no X-ray diffraction in flight. Crystal quality is known only after return.
• The bay microscope cannot reliably resolve particles of a few microns, so the in-flight size data are qualitative. The full particle size distribution needs ground instruments.
• Microgravity helps only some proteins. In JAXA's flights 1 to 5, 40 of 215 samples (19%) gave good results, and success needed highly homogeneous samples in viscous solutions.
• Sample volumes are millilitres per well. This is a research and formulation-development service, not drug manufacturing.
• The bay range is 4 to 45 C. Melt-based small-molecule processes such as Varda's W-1 ritonavir run (131 C melt, 80 C growth) are out of scope.
• Arm motion and any thruster use raise the g-level. Growth wells need quiet periods, and the timeline must be shared with other bays.
• LELP-1 is a design in a digital twin. None of this has flown, and all LELP-1 numbers are our estimates.