Preconditioning Single High-Dose Palifermin Alters the Posttransplant Inflammatory Cytokine Profile

Palifermin is a truncated form of human recombinant keratinocyte growth factor (KGF) that binds to the FGF receptor 2b expressed in epithelia including that of the epidermis, oral and GI mucosa, and thymus. In animal models, the cytoprotective and regenerative effects of KGF showed efficacy in controlling acute and chronic graft-versus-host disease (A/C GVHD), but these were not demonstrated in subsequent clinical studies using the FDA-approved dosing schedule for oral mucositis prevention (60 µg/kg/day for 3 consecutive days).

The current study aims to investigate alterations in immune cell reconstitution and cytokine expression among patients (n=31) participating in the ongoing prospective open-label phase 1/2 trial NCT02356159. This trial evaluates the incidence of severe CGVHD (primary objective of phase 2) following the addition of a single high dose of palifermin to GVHD prophylaxis with TMS (tacrolimus, methotrexate, sirolimus). Four different dose levels of palifermin (DL1: 180 µg/kg; DL2: 360 µg/kg; DL3: 540 µg/kg; DL4: 720 µg/kg) were tested on day −7 in the phase 1 part of the trial, with the recommended phase 2 dose being 720 µg/kg. All patients received cyclophosphamide (total 4.8 g/m²) and fludarabine (total 120 mg/m²) as conditioning on days −6 to −3 followed by infusion of an 8/8 HLA-matched unrelated donor peripheral blood cell graft on day 0. Results of correlative studies were compared with patients of the identical TMS treatment arm of the NCT00520130 study without palifermin (n=31). In the DL4 group, a previous interim analysis revealed no cases of classic (day +100) AGVHD II-IV in 16 patients (P=0.014), whereas the TMS group showed a 22.6% (95% CI: 9.8% to 38.6%) incidence (Schulz et al. Cell Ther Transplant. 2023;29(2):S258).

T, B and NK cells were routinely measured by flow cytometry at days +14, +28, +60, +100, +180, +365, +730. The V-PLEX human cytokine 36-plex kit and U-PLEX assays of human BAFF, CXCL9 and IL1RL1/ST2 (all MSD, Rockville, MD) were used to measure cytokine levels in plasma at days −8, 0, +14, +28, +60, +100. The measures at various time points were compared between two treatment groups using multiple Mann-Whitney tests, and the false discovery rate approach was applied with Q=0.05. Comparison between the four DL groups and the TMS group was performed using the Kruskal-Wallis H-test and Dunn's post-hoc test, with a significance threshold set at P<0.05. The statistical analyses were conducted using GraphPad Prism 9.

In comparison to patients receiving TMS only, those treated with KGF exhibited reduced NK cell counts at day +28 (Q=0.0155) and increased B cell counts from day +60 (Q<0.01) onwards. However, there were no differences in the absolute numbers of CD3+, CD4+, and CD8+ T cells between patients from both trials. Additionally, no apparent dose-response relationship was observed.

KGF-treated patients showed significantly reduced plasma levels of proinflammatory cytokines, including TNF-α at day 0, TNF-β at days 0, +14, +28, IL-12/IL23p40 at days 0 and +14, and CXCL9 at days 0 and +14, compared to patients receiving TMS only. Notably, levels of homeostatic IL-7, previously linked to AGVHD, were significantly lower in KGF-treated patients from day +28 (TMS vs. DL4, P=0.002) to +100. There was a trend towards lower levels of IL-22 at days 0 and +14 (both unadjusted P<0.05, Q>0.05) in KGF-treated patients. Other proinflammatory biomarkers showed increased levels in KGF-treated patients: IL-15 at day 0 (Q=0.0121), BAFF at days +14 and +28 (both Q<0.01), and ST2 at day 0 and day +14 (both Q<0.01). As reported previously by others, patients who developed classic or late onset AGVHD II-IV without prior relapse up to day +180 had higher ST2 levels at day +14 compared to patients without AGVHD II-IV (P=0.03). Here, this association was mainly observed in patients from the TMS and DL1 groups (6/8 tested patients with any AGVHD II-IV).

The administration of a single high dose of palifermin (KGF) prior to conditioning treatment resulted in a notably distinct cytokine profile, characterized by a reduction in several GVHD associated pro-inflammatory cytokines, consistent with KGF’s proposed cytoprotective effect. Further investigations focusing on GI microbiome and immune cell subsets are needed to elucidate the consequences of cytokine alterations induced by KGF on immune cell reconstitution.

This research was supported by the Intramural Research Program of the NIH, NCI, CCR.