Peritransplant palifermin use and lymphocyte recovery after T‐cell replete, matched related allogeneic hematopoietic cell transplantation
Authors: Romee Rizwan, John E. Levine, Todd DeFor, James L.M. Ferarra, Daniel J. Weisdorf, Bruce R. Blazar, Michael R. Verneris
Journal: American Journal of Hematology (2011)

Allogeneic hematopoietic cell transplantation (allo-HCT) is often the only curative option for people with otherwise fatal hematologic malignancies. As the number of allo-HCT procedures continues to increase [1], it is increasingly clear that a major obstacle to success is delayed immune recovery, which puts patients at risk for a wide variety of opportunistic infections [2-8]. Additionally, rapid early lymphocyte recovery may serve as a surrogate predictor of better transplant outcomes. Robust recovery of absolute lymphocyte counts (ALC) early after transplantation is associated with improved survival following autologous, sibling, unrelated bone marrow, peripheral blood, and umbilical cord blood transplantation [9-15]. There is a clear need to develop strategies to accelerate and improve immune reconstitution (IR). Several novel approaches have been successfully tested in preclinical animal models and early human clinical trials. These include pretransplant androgen ablation, keratinocyte growth factor (KGF), and a p53 inhibitor or post-transplant administration of interleukin (IL)-7, IL-15, growth hormone, or insulin-like growth factor-1 [16-20]. KGF is a potent growth factor belonging to the fibroblast growth factor family that stimulates epithelial growth and differentiation, without affecting the nonepithelial cells that lack the fibroblast growth factor receptor 2-IIIb receptor. In the thymus, KGF is produced locally by mesenchymal cells and acts on thymic epithelial cells (TECs) [18, 21]. Through its trophic effects on TECs, KGF facilitates normal thymopoiesis, which is required for naïve T cell generation [22]. In murine allo-HCT models, KGF treatment improved thymopoiesis and enhanced T cell IR [18, 23]. In a non-human primate model of autologous hematopoietic cell rescue following myeloablation, peritransplant KGF administration led to the preservation of thymic architecture for up to 12 months after HCT [24]. In the same study, KGF-treated animals had higher frequencies of naïve T cells compared to the control group. Another preclinical study that combined KGF with androgen depletion led to enhanced thymopoiesis characterized by a broad V-beta T cell repertoire [25]. To assess the GVHD protective potential of KGF, a phase I/II randomized, placebo-controlled trial of recombinant human KGF (palifermin) was performed from 2000 to 2003 in 100 patients undergoing T-cell replete, matched related donor (MRD) allo-HCT following myeloablative conditioning [26, 27]. The focus of this study was to determine the impact of KGF on GVHD. Detailed IR was not studied within the trial. Because ALC is associated with transplant outcomes [9-15], we questioned whether there might be differential effects of KGF on early ALC recovery. Here, we report our retrospective analysis using data from our earlier trial to assess the effects of peritransplant use of palifermin on ALC recovery at following HCT. This is the first report analyzing the results of palifermin and lymphocyte recovery in humans. We tested ALCs after transplant in the palifermin and placebo treatment groups. As shown in Fig. 1a, the median ALC at days 30, 60, and 100 after transplant did not significantly differ in the palifermin versus placebo arms (600 × 106/L vs. 600 × 106/L; P = 0.26, 500 × 106/L vs. 600 × 106/L; P = 0.86, 600 × 106/L vs. 700 × 106/L, P = 0.19). Likewise, there was no influence of the palifermin dose and subsequent ALC recovery post-transplant ALC (Fig. 1b). As well, palifermin did not impact ALC based on the conditioning regimen (Bu/Cy vs. Cy/total body irradiation [TBI]), recipient age, and the presence of acute GVHD (aGVHD; data not shown). As previously reported, in this trial, palifermin use was not associated with shorter time to engraftment, aGVHD, survival, or infectious complications after transplant. However, palifermin modestly decreased mucositis [26, 27]. Post-transplant ALC in palifermin and placebo groups. (a) Median and interquartile range of ALC for the placebo (open bars) and palifermin (shaded bars) at days 30, 60, and 100 after transplantation. The median ALC at the three time points in the two groups were 600 × 106/L versus 600 × 106/L (P = 0.26), 600 × 106/L versus 500 × 106/L (P = 0.86), and 700 × 106/L versus 600 × 106/L (P = 0.19), respectively. (b) Comparison of median and interquartile ranges of days 30, 60, and 90 ALCs at various doses of palifermin with placebo. Based on prior studies [9-15], we also examined whether differential lymphocyte counts were associated with transplant outcomes. Patients with an ALC above the median at D+30 (>600 × 106/L) showed a trend for improved progression-free survival (PFS) (49% [95% confidence interval (CI), 32–65%] vs. 29% [95% CI 16–43%], P = 0.07; Fig. 2a). There was no association between D+30 ALC and disease recurrence (28% [95% CI 14–42%] vs. 23% [95% CI 10–36%], P = 0.6; Fig. 2b). There were trends toward less 2-year treatment related mortality (TRM) (18% 95% CI [6–30%] vs. 35% [95% CI 20–50%], P = 0.1) and grade II–IV aGVHD (31% [95% CI 17–45%] vs. 47% [95% CI 32–62%], P = 0.14) in patients with an ALC > 600 at D+30 after transplant (Fig. 2c,d). These rates were unaffected by KGF therapy. Transplant outcomes based on ALC at day 30.Outcomes were measured for patients above or below the median ALC (i.e., >600 × 106/L or ≤600) at day 30. (a) PFS at day 30 was 49% versus 29%, respectively (P = 0.07). (b) The cumulative incidence of relapse was 28% versus 23%, respectively (P = 0.6). (c) Two-year TRM was 18% versus 35%, respectively (P = 0.1). (d) Grade II-IV aGVHD was 31% versus 47% (P = 0.14). In this first allotransplant palifermin dose escalation trial, using ALC as a marker for IR, we found that peri-transplant palifermin had no impact on ALC at days 30, 60, or 100 after allo-HCT. These results differ from rodent studies [22, 25] and a non-human primate study [24] where KGF was associated with protection of TECs from radiation-induced damage, resulting in improved thymopoiesis and peripheral IR after transplant. Numerous explanations may account for our findings including suboptimal palifermin dose or dosing schedule, existing pretransplant chemotherapy-induced TEC damage or a limited potency of this agent on human TECs. ALC is a relatively crude marker for IR and the lack of information on various T cell subsets, T cell receptor Vβ repertoire, and newly formed T cells (i.e., T Cell Receptor Excision Circles) limits our ability to detect any effects of palifermin on the naïve versus homeostatically expanded T cells. It is possible that the early lymphocyte recovery after T-cell replete HCT is not reflective of thymic output and may be more related to homeostatic proliferation of existing T cells. In this scenario, ALC may be unaffected by palifermin. In addition, significant aGVHD occurred in nearly half the patients in this study. This complication is associated with thymic injury and requires extended immunosuppressive therapy. Thus aGVHD (or its treatment) might have confounded any potential of palifermin to augment IR. However, there was no significant difference in ALCs between the palifermin- and placebo-treated groups, even after excluding patients with aGVHD (data not shown). However, it is still possible that the GVHD prophylaxis itself (which were not used in the preclinical models) may have blunted any potential benefit of palifermin on lymphocyte recovery, considering that most GVHD prophylactic agents inhibit T cell production and expansion. Previous studies show a positive correlation between early ALC and transplant with outcome measures [9, 14, 28]. Although the clinical impact of ALC recovery was only a secondary aim of this study, we observed a trend toward improved PFS and lower TRM in patients above the median ALC at day 30, consistent with other reports [13-15, 28]. Interestingly, a lower day 30 ALC was associated with a trend toward more frequent grade II–IV aGVHD. Thus, it is possible that before becoming clinically evident, aGVHD is heralded by delayed recovery of ALC. Delayed IR continues to be a major problem after allo-HCT. Based on this analysis, palifermin alone is unlikely to significantly improve post-allo-HCT immune recovery, at least following T-cell replete allo-HCT. In recent years, there have been significant advances in understanding the mechanisms behind delayed IR, and some novel interventions have been successful in preclinical models (reviewed in Ref.29). Perhaps, strategies combining two or more agents, shown to be promising in preclinical models, may be needed to overcome the profound immune deficiency which follows allo-HCT. Patient and transplant characteristics have been reported previously [26, 27]. A total of 100 patients were enrolled in this study and randomized to receive placebo (n = 31) or palifermin (n = 69). Two patients in the palifermin group did not undergo transplantation and were excluded. As shown in Table I, patient demographics and underlying diagnosis were well matched between the two groups. Median follow-up among survivors is 4.1 years (range: 2–6.1 years) for both groups. All patients received allo-HCT from HLA-identical sibling donors after myeloablative conditioning, which included 120 mg of cyclophosphamide and 1,320 cGy of fractionated TBI at University of Minnesota or 16 mg/kg of oral busulfan and 60 mg/kg of cyclophosphamide (Bu/Cy) at the University of Michigan. A calcineurin inhibitor (cyclosporine or tacrolimus) and methotrexate (15 mg/m2 on day 1 and 10 mg/m2 on days 3, 6, and 11) were used for GVHD prophylaxis. This was a randomized, double-blind, placebo-controlled, dose-escalation study. Three cohorts receiving increasing palifermin doses were sequentially enrolled, with each cohort randomized to achieve balance within each study site and in each cohort. Stratification was based on conditioning regimen and patient age. A total of 98 patients completed this study, with a 1:2 randomization between placebo (n = 31) and study drug (n = 67). All treatment cohorts received 3 days of palifermin at 40 mg/kg (n = 8) or 60 mg/kg (n = 61) prior to the start of conditioning (days −11 to −9) and then received the same palifermin dose on 3 consecutive days weekly (first 3 days of a week) staring on day 0 and extending for 1 (n = 18), 2 (n = 14), or 3 (n = 37) weeks after transplant. Thus, the total palifermin dose was 240 mg/kg in the lowest dose cohort and 720 mg/kg for the highest dose cohort. For the current analysis, ALCs were extracted from the patient medical records on days 30, 60, and 100 (±7 days) after obtaining institutional review board approvals at both study sites. Statistical comparisons of the distribution of ALC over time were performed by examining the median, interquartile ranges, and ranges of ALC at days 30, 60, and 100 post-transplant and performing either a general Wilcoxon or Kruskal-Wallis test by a number of factors: KGF group (placebo vs. KGF), placebo dose, presence of grade II-IV aGVHD, conditioning and age. Outcomes by ALC were analyzed by simply dividing cohorts by the median ALC and estimating the outcomes of the two groups using Kaplan-Meier estimates for overall survival and PFS (34) and the cumulative incidence (CI) for relapse, nonrelapse mortality, and GVHD (35). Analyses were performed using SAS 9.2 (SAS Institute) and R 2.4 statistical software. Romee Rizwan and Michael R. Verneris planned data analysis, reviewed and complied data, and wrote paper; Todd DeFor performed statistical analysis; John Levine planned the original trial, provided data, and edited the manuscript; and James Ferarra, Daniel Weisdorf, and Bruce R. Blazar planned the original clinical trial and edited the manuscript.