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Table 2 Results from drug substance release testing (n = 66 batches derived from 7 donors)

From: Process data of allogeneic ex vivo-expanded ABCB5+ mesenchymal stromal cells for human use: off-the-shelf GMP-manufactured donor-independent ATMP

Parameter Specification Result Deviations
absolute %
ABCB5+ cell content ≥ 90% 97.72 ± 1.88% 1a 1.5a
Mycoplasma Not detectable (< 10 CFU/ml) Not detectable in 65/66 batches 1 1.5
Endotoxin level ≤ 2 EU/ml ≤ 2 EU/ml in 66/66 batches 0 0
Live cell count n.a.b 275.33 × 106 n.a.b n.a.b
Deviation of live cell count from expected valuec ≤ 30% ≤ 30% in 46/49 batchesd 3 6%d
Cell vitalitye ≥ 90% 98.60 ± 0.62% 0 0
Cell viabilityf ≥ 90% 99.45 ± 0.64% 0 0
CD90+ cell content ≥ 90% 99.45 ± 0.50% 0 0
Bead residues ≤ 0.5% 0.04 ± 0.05% 0 0
Microbiological control No growth No growth in 66/66 batches 0 0
IL-1RA secretion > 125 pg/ml and ratiostim/unstim > 1 > 125 pg/ml and ratiostim/unstim > 1 in 66/66 batches 0 0
VEGF secretion > 46.9 pg/ml > 46.9 pg/ml in 66/66 batches 0 0
Angiogenic differentiation Capillary structures in one or both seeded cell concentrations positive in 63/66 batches 3 4.5%
  1. Numeric results are given as mean ± SD
  2. n.a. not applicable
  3. aFor one batch, measurement procedure was not fully GMP-conform. Although this did not affect the result, the batch was not released for drug production
  4. bAcceptance criteria for cell count are only defined for the aliquots into which the drug substance batches are divided for cryostorage, not for the batch as a whole
  5. cExpected value = sum of the live cell counts of all ABCB5+ cell isolates that were pooled to produce the drug substance batch
  6. dThe criterion “Deviation of live cell count from expected value” was implemented only from donor 4 on, which is the reason for the lower sample number (n = 49)
  7. eVitality was defined as percentage of live cells, defined as propidium iodide-excluding cells
  8. fViability was defined as percentage of metabolically active cells, defined as cells converting calcein acetoxymethylester to calcein