Periodic Reporting for period 5 - RETHRIM (Restoring tissue regeneration in patients with visceral Graft versus Host Disease.)
Reporting period: 2021-01-01 to 2021-12-31
Allogeneic stem cell transplantation is a potentially curative treatment for a variety of haematological disorders. While offering the potential for cure, one of the major complications after transplantation is the occurrence of acute Graft-versus-Host Disease (aGvHD), which in its severe form caries a mortality risk of up to 75%. A number of phase I/II trials have indicated that use of third-party Mesenchymal Stromal Cells (MSC) might be an effective therapy for GvHD. However, no definitive proof of effectiveness through double-blind placebo controlled multicentre studies has been obtained. The RETHRIM phase III clinical trial was aimed at setting a new standard for the treatment of GvHD. MSC regenerative therapy was employed to determine its potential to improve the rates of remission and overall survival and to improve quality of life.
In addition to the clinical trial, quality of life, health technology assessments and ethical studies regarding patient access to care were to be performed. Output from these studies were foreseen to allow the consortium to formulate a set of measures to convince health authorities, regulatory bodies and insurance companies on the usefulness of MSC therapy and provide suggestions and recommendations for changes in clinical practise, legislation and regulation of MSC regenerative therapy.
However, due to insufficient accrual of patients, the trial did not have sufficient power to detect the anticipated difference between the two treatment arms. With 42 patients included, no statistically significant effect of MSC infusions on aGvHD response on day 28, overall survival, or safety could be demonstrated.
In addition to the clinical trial, quality of life, health technology assessments and ethical studies regarding patient access to care were to be performed. Output from these studies were foreseen to allow the consortium to formulate a set of measures to convince health authorities, regulatory bodies and insurance companies on the usefulness of MSC therapy and provide suggestions and recommendations for changes in clinical practise, legislation and regulation of MSC regenerative therapy.
However, due to insufficient accrual of patients, the trial did not have sufficient power to detect the anticipated difference between the two treatment arms. With 42 patients included, no statistically significant effect of MSC infusions on aGvHD response on day 28, overall survival, or safety could be demonstrated.
The Phase III Randomized Double-blind Multi-center HOVON-113 Clinical trial on Treatment of Severe Steroid-refractory Acute GvHD with Mesenchymal Stromal Cells was conducted from January 2015 to January 2020 in the Netherlands, Germany, Spain, Italy, and Belgium. 42 patients were enrolled and randomized to receive either placebo or mesenchymal stromal cells. Unfortunately the trial had to be terminated prematurely due to low accrual. Several mitigation steps were taken to increase patient enrolment in the study but the numbers remained low. The intended number of patients to be enrolled was not reached. This hampered statistical significance for all analysis in the other work packages.
For the drug product, a fully harmonized production protocol was introduced and a detailed IMPD provided. All MSC products were generated, for the reduced number of 42 patients, before recruitment was terminated. To evaluate the purity and identity of the drug product, an 8-color flow cytometry panel based on the Euroflow platform was developed. A potency assay was designed. For both assays a patent was submitted which is currently under consideration at EPO.
To study the immune reconstitution profile, a dedicated sampling collection and handling protocol was developed. Screening of whole blood and biopsy samples for immune markers was performed using CyTOF analysis. Two marker panels (T-cell and non T-cell panels), consisting of lineage-specific markers as well as a set of differentiation, activation and homing markers, allowed for the identification of distinct innate and B cell populations as well as effector T cell subsets with tissue destructive potential which remained persistently high in aGvHD patients who failed to respond to MSC therapy. These cells are equipped with receptors for migration towards aGvHD tissues (GI-tract and skin).
RNA sequencing of PBMC obtained at various time intervals after MSC infusion was performed. This resulted in the identification of a robust immunological neutrophil activation signature in poorly-surviving patients, while an eligibility signature associated with outcome, could not be established. Neutrophil enrichment changed from immature to a granule-rich inflammatory phenotype. Patients who ultimately not survived, were defined by strong neutrophil activation at day 7 post treatment, that persisted throughout the duration of the study. Soluble CD163 was found to be elevated in plasma of the deceased patient subgroup, possibly reflecting the uncontrollable inflammatory responses occurring in these patients. This was supported by the increase of other pro-inflammatory biomarkers such as CXCL9, CD40, altogether indicating the severity of tissue inflammation and the degree of innate and adaptive immune cell activation.
For the drug product, a fully harmonized production protocol was introduced and a detailed IMPD provided. All MSC products were generated, for the reduced number of 42 patients, before recruitment was terminated. To evaluate the purity and identity of the drug product, an 8-color flow cytometry panel based on the Euroflow platform was developed. A potency assay was designed. For both assays a patent was submitted which is currently under consideration at EPO.
To study the immune reconstitution profile, a dedicated sampling collection and handling protocol was developed. Screening of whole blood and biopsy samples for immune markers was performed using CyTOF analysis. Two marker panels (T-cell and non T-cell panels), consisting of lineage-specific markers as well as a set of differentiation, activation and homing markers, allowed for the identification of distinct innate and B cell populations as well as effector T cell subsets with tissue destructive potential which remained persistently high in aGvHD patients who failed to respond to MSC therapy. These cells are equipped with receptors for migration towards aGvHD tissues (GI-tract and skin).
RNA sequencing of PBMC obtained at various time intervals after MSC infusion was performed. This resulted in the identification of a robust immunological neutrophil activation signature in poorly-surviving patients, while an eligibility signature associated with outcome, could not be established. Neutrophil enrichment changed from immature to a granule-rich inflammatory phenotype. Patients who ultimately not survived, were defined by strong neutrophil activation at day 7 post treatment, that persisted throughout the duration of the study. Soluble CD163 was found to be elevated in plasma of the deceased patient subgroup, possibly reflecting the uncontrollable inflammatory responses occurring in these patients. This was supported by the increase of other pro-inflammatory biomarkers such as CXCL9, CD40, altogether indicating the severity of tissue inflammation and the degree of innate and adaptive immune cell activation.
A conceptual decision-analytic model was developed to simulate the disease process of patients with steroid-refractory acute graft-versus-host disease. This model formed the conceptual baseline for a cost-effectiveness analysis comparing Mesenchymal Stromal Cells (MSC) to placebo for the treatment of GvHD. According to the analyses it can be concluded that the administration of the MSC in patients with steroid-refractory aGVHD could be cost-effective at a “willingness to pay” of € 80,000 per QALY gained. However, the estimated probability of response within the first 28 days post treatment, as well as the assumed long-term survival of these patients influenced the results substantially. The uncertainty in the estimation of these parameters can only be reduced by gathering more data, preferably from clinical trials or alternatively from patient registry data. Neither are currently available. Given this uncertainty of the model outcomes, provision of a “convincing health management plan” is unfortunately futile. Future (clinical) studies could help reducing the uncertainty of the clinical parameters by recruiting a larger population and extending the trial follow-up period.
The project dedicated considerable attention to ethical analysis of the method adopted in this trial involving placebo-controls. The analysis justified their use in both adult and paediatric populations in the light of existing international ethical guidelines. Besides placebo-control use, other ethical aspects were analysed such as: difficulties involved in obtaining Europe-wide approval for Phase III randomized placebo-controlled trials; hospital exemption; strong and weak sides of academia-initiated trials as compared to industry-initiated trials; influence of internationally emerging “conditional approval” programs; A manuscript was produced addressing these issues, highlighting the need for a debate about the interpretation and application of current ethical guidelines. Recommendations were developed for conducting randomized placebo-controlled trials where the benefit of the potentially successful experimental treatment amounted to potentially life-saving therapy and the efficacy of existing “best proven” therapy was poor. These recommendations were in no way concurring with the existing ethical guidelines and were rather intended as a checklist of specific issues to be considered in these difficult cases and not an imperative list of steps applicable in all situations. Each recommendation was accompanied by a brief explanatory text of the rationale why it was important to be considered.
The RETHRIM consortium initiated the EU-MSC2 meeting series which assembled all consortia working on MSC therapy. The EU-MSC2 meeting were a success, 10 EU consortia working on MSC therapy joined to discuss progress in the field, EU project officers attended the meetings and participation of regulatory bodies, patient representatives and policy makers allowed for lively discussions to further the field.
The project dedicated considerable attention to ethical analysis of the method adopted in this trial involving placebo-controls. The analysis justified their use in both adult and paediatric populations in the light of existing international ethical guidelines. Besides placebo-control use, other ethical aspects were analysed such as: difficulties involved in obtaining Europe-wide approval for Phase III randomized placebo-controlled trials; hospital exemption; strong and weak sides of academia-initiated trials as compared to industry-initiated trials; influence of internationally emerging “conditional approval” programs; A manuscript was produced addressing these issues, highlighting the need for a debate about the interpretation and application of current ethical guidelines. Recommendations were developed for conducting randomized placebo-controlled trials where the benefit of the potentially successful experimental treatment amounted to potentially life-saving therapy and the efficacy of existing “best proven” therapy was poor. These recommendations were in no way concurring with the existing ethical guidelines and were rather intended as a checklist of specific issues to be considered in these difficult cases and not an imperative list of steps applicable in all situations. Each recommendation was accompanied by a brief explanatory text of the rationale why it was important to be considered.
The RETHRIM consortium initiated the EU-MSC2 meeting series which assembled all consortia working on MSC therapy. The EU-MSC2 meeting were a success, 10 EU consortia working on MSC therapy joined to discuss progress in the field, EU project officers attended the meetings and participation of regulatory bodies, patient representatives and policy makers allowed for lively discussions to further the field.