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Phelan-McDermid syndrome (PMS) or 22q13.3 deletion syndrome is a rare neurodevelopmental disorder with at least 60 children and 35 adults diagnosed in the Netherlands. Clinical features are moderate to severe intellectual disability and behavioural problems in the autism spectrum. Other researchers had observed a beneficial effect of intranasal insulin on development and behaviour in a pilot study in six children with PMS. To validate this effect, we conducted a randomized, double-blind, placebo-controlled clinical trial using a stepped-wedge design. From March 2013 to June 2015, 25 children aged 1-16 years with a molecularly confirmed 22q13.3 deletion including the SHANK3 gene participated in the clinical trial for a period of 18 months. Starting 6 months before the trial, children were systematically assessed for cognitive, language and motor development and for adaptive, social and emotional behaviour every 6 months. The second, third and fourth assessments were followed by daily nose sprays containing either intranasal insulin or intranasal placebo for a 6-month period. A fifth assessment was done directly after the end of the trial. Intranasal insulin did not cause serious adverse events. It increased the level of developmental functioning by 0.4-1.4 months per 6-month period, but the effect was not statistically significant in this small group. We found a stronger effect of intranasal insulin, being significant for cognition and social skills, for children older than 3 years, who usually show a decrease of developmental growth. However, clinical trials in larger study populations are required to prove the therapeutic effect of intranasal insulin in PMS.

Low-toxicity conditioning regimens prior to bone marrow transplantation (BMT) are widely explored. We developed a new protocol using hematopoietic growth factors prior to low-dose total body irradiation (TBI) in recipients of autologous transplants to establish high levels of long-term donor cell engraftment. We hypothesized that treatment of recipient mice with growth factors would selectively deplete stem cells, resulting in successful long-term donor cell engraftment after transplantation. Recipient mice were treated for 1 or 7 days with growth factors (stem cell factor [SCF] plus interleukin 11 [IL-11], SCF plus Flt-3 ligand [FL], or granulocyte colony-stimulating factor [G-CSF]) prior to low-dose TBI (4 Gy). Donor cell chimerism was measured after transplantation of congenic bone marrow cells. High levels of donor cell engraftment were observed in recipients pretreated for 7 days with SCF plus IL-11 or SCF plus FL. Although 1-day pretreatments with these cytokines initially resulted in reduced donor cell engraftment, a continuous increase in time was observed, finally resulting in highly significantly increased levels of donor cell contribution. In contrast, G-CSF treatment showed no beneficial effects on long-term engraftment. In vitro stem cell assays demonstrated the effect of cytokine treatment on stem cell numbers. Donor cell engraftment and number of remaining recipient stem cells after TBI were strongly inversely correlated, except for groups treated for 1 day with SCF plus IL-11 or SCF plus FL. We conclude that long-term donor cell engraftment can be strongly augmented by treatment of recipient mice prior to low-dose TBI with hematopoietic growth factors that act on primitive cells.

Busulfan (1,4-butanediol dimethanesulfonate, BU) is relatively unique among other standard chemotherapy compounds in its ability to deplete noncycling primitive stem cells in the host and consequently to allow for high levels of long-term, donor-type engraftment after bone marrow transplantation (BMT). Such a property explains why this drug can be used as an alternative to total body irradiation in preparative regimes for BMT. However, as with radiation, BU conditioning is still troubled by severe toxicities that limit its applications to suboptimal drug doses. These problems stress the need for other BMT-conditioning drugs that are better tolerated and more selectively targeted toward normal and malignant hematopoietic stem cells. We have therefore compared the effects of various novel dimethanesulfonate compounds (related to BU) in terms of their toxicity to different stem cell subsets in vivo and in vitro and their ability to provide for long-term donor bone marrow engraftment using the congenic glucose-6-phosphate isomerase type 1 marker. Introduction of a benzene or cyclohexane ring in some of these drugs affords rigidity to the molecule and restricts the spatial positioning of the alkylating groups. Among 25 different compounds thus far tested at single doses, PL63 [cis-1,2-(2-hydroxyethyl) cyclohexane dimethanesulfonate] proved to be the most effective in providing for hematopoietic engraftment. The transisomer of the same compound gave significantly less engraftment and was comparable with the effects of dimethylbusulfan and Hepsulfam. The engraftment data correlated well with the depletion of different bone marrow stem cell subsets in the host as measured using the cobblestone area forming cell assay. The extent of stem cell depletion could not be explained on the basis of the distance and orientation of the two alkylating groups. Pharmacokinetic data, however, indicate that there is a correlation between biological activity and plasma levels reached. The diverse cytotoxic effects shown by these novel analogues of BU have provided a basis for relating biological activity with pharmacokinetic properties rather than with structural properties such as distance and orientation of the two alkylating groups. The identification of highly active compounds such as PL63 offers an opportunity for further developing other closely related drugs for potential application in clinical BMT conditioning therapy.

The tetrapeptide AcSDKP (Goralatide) is a cytokine with known inhibitory effects on cell proliferation. Many purging agents used in autologous bone marrow transplantation protocols, including hyperthermia, preferentially kill cycling cells. A pretreatment with Goralatide offers a possibility to reduce the haemotoxicity in many purging settings. The impact of Goralatide on the hyperthermic purging protocol was investigated in normal and myeloid leukaemic (SA8) murine cells. The median survival time after transplantation (i.e. leukaemia incidences) was used as an in vivo parameter to determine the effects on leukaemic cells. The hyperthermic effect on normal and leukaemic cells was also investigated in vitro using the cobblestone area-forming cell (CAFC) assay. A heat treatment of 90 min at 43 degrees C resulted in a 4-log depletion of leukaemic stem cells. For normal progenitor cells (CFU-GM) a 2-log cell kill was shown. The reduction in proliferative activity of the CFU-GM after an 8 h incubation with 10(-9) M Goralatide resulted in a decrease in the heat sensitivity of the progenitor subset to approximately a 1-log cell kill. The leukaemic precursor cells seem insensitive to Goralatide inhibition, implicating an increase in the therapeutic window of the hyperthermic purging protocol. Finally, simulated remission bone marrow (5% leukaemic blasts) was incubated with Goralatide followed by a heat treatment of 90 min at 43 degrees C. Lethally irradiated (10 Gy) mice transplanted with heat-treated remission bone marrow (10(6) normal bone marrow cells versus 5 x 10(4) leukaemic cells) died of aplasia while Goralatide-pretreated remission bone marrow could rescue the irradiated mice without revealing leukaemic engraftment. These findings confirmed the enhanced protection against hyperthermia of the normal haemopoietic subsets by Goralatide and thus increased the success of the hyperthermic purging protocol.

The effect of stem cell factor (SCF) given at 24, 12 and 2 h before either 5-fluorouracil (5-FU) or total-body irradiation (TBI) was investigated on a range of bone marrow hemopoietic cell subsets that included primitive stem cells capable of long-term repopulation in bone marrow transplant (BMT) recipients. At 24 h after treatment, the femoral content of transient and permanent repopulating stem cell subsets was assessed from the frequency of early- and late-developing cobblestone area-forming cells (CAFCs) growing in stroma-associated cultures. At this time untreated 3 x 10(6) congenically marked donor bone marrow cells (B6-Gpi-Ia-->B6-Gpi-Ib) were transplanted and the level of erythroid engraftment was followed over 1 year. Analysis of the frequencies of CAFCs in host bone marrow after treatment with SCF demonstrated a remarkable increase in the number of early-developing CAFC subsets by about 10-fold. At the same time SCF conferred a sensitization of these subsets after treatment with 5-FU, which indicated an enhanced proliferative activity. The SCF-induced increase in the number of progenitor cells, however, was the more dominant process in the irradiated animals, resulting in less overall depletion of CAFCs. These contrasting results provide an explanation for the sensitization by SCF of 5-FU-induced lethality and its converse protection against radiation-induced lethality as reported by others. Nevertheless, the number of the more primitive CAFC subsets appearing at 28 and 35 days in culture and their sensitivity to 5-FU or radiation remained unaffected by this short SCF treatment. The number of CAFCs that remained in the bone marrow largely predicted the subsequent patterns of donor marrow engraftment in the treated BMT recipients: SCF enhanced short-term engraftment after treatment with 5-FU while it reduced the need for short-term engraftment after irradiation. Only irradiation afforded long-term engraftment through depletion of primitive host stem cells, and this was moderately improved by prior treatment with SCF.