Intestinal organoids
Intestinal organoids are derived from rectal biopsies of individual
patients. The biopsied cells form three dimensional structure of
epithelial cells in vitro. As these intestinal cells have CFTR channels,
in cells with functioning CFTR, the addition of forskolin will open the
CFTR channels allowing for water uptake and the organoid will swell. As
would be expected, in the absence of a modulator, the organoid will not
exhibit forskolin-induced swelling If a modulator is present and
effective, organoid swelling will be observed. Researchers have used
organoids to test the effects of modulators on individual patients.
Organoids include the specific cells of a patient in a three dimensional
in vitro model, which can potentially be compared to the patient’s
individual clinical improvements with a specific modulator therapy.
There have been two studies using organoids to study CFTR modulators in
2020. One group, mentioned above in the LCI endpoint section, studied
the effectiveness of iva and compared the clinical and in vitroorganoid endpoints18. In the randomized
placebo-controlled, crossover study of 38 subjects (37 completed), with
either the 3849+10kbCT or D1152H mutation, intestinal organoids cultures
were successfully established in 29 out of 33 biopsies, but only 25
intestinal organoid cultures met quality control standards. Swelling of
organoids (indicating appropriate action of iva) occurred in 23 out of
25 patients, but there was no correlation (using Pearson correlation
analysis) between the degree of clinical improvement (sweat chloride,
LCI, FEV1pp) and the degree of swelling of the organoids for these
subjects with the D1152H or 3849+10kbCT mutation. Of note, the clinical
improvements were small and measured over an 8 week period. In a
separate study of patients with the A455E mutation, based on in
vitro organoid data, 20 pwCF over age 12 were included in a randomized
trial of lum/iva in the Netherlands with cross-over design for 8
weeks20. With lum/iva, FEV1pp did not change
significantly (0.1%). CFQ-R respiratory domain increased by 3.5 points,
but this is not considered clinically significant. Sweat chloride
decreased significantly by -7.8mmol/L, p=0.004, but this again may not
show a biochemically relevant change, as the decreases in sweat chloride
have been much greater with even lum/iva in F508del homozygotes, on the
order of 20mmol/L. In vitro organoid response was seen but not
correlated with sweat chloride or FEV1pp20, similar to
the above findings. Both authors conclude that the use of organoids are
of potential benefit to identify modulator responsive mutations, but may
not predict the degree of response the patient will have in terms of
clinical parameters like FEV1pp or sweat
chloride18,20. One researcher postulated that a
correlation between intestinal organoids and clinical phenotypes may not
exist, as the clinical phenotypes took years to establish and may not be
fully reversed by CFTR modulators, or may be impacted by other non-CFTR
dependent factors21. It will be interesting to see the
use of intestinal organoids for CFTR modulator research in the future.