**4.2 HBO in UCB transplantation**

Based on the previously mentioned pre-clinical data, a pilot clinical trial investigating the safety of HBO in UCB transplant was initiated. Patients considered

**Figure 5.**

*Clinical trial schema incorporating hyperbaric oxygen (HBO) into hematopoietic cell transplantation.*

**157**

ml+/−31.68, *p* = 0.004).

**Table 1.**

ery slows down disease progression.

*Effect of Hyperbaric Oxygen on Hematopoietic Stem Cell Transplantation*

for either standard myeloablative conditioning (MAC) (higher intensity chemotherapy and radiation) or standard reduced intensity conditioning (RIC) (lesser intensity chemotherapy and radiation) UCB transplantation were enrolled. In this study, HBO treatment was administered on day 0 of the transplant. The treatment consisted of exposure to 100% oxygen at 2.5 ATA for a total of 2 hours, in a single see-through hyperbaric chamber. Six hours from the start of HBO, single or double UCB units are infused, and patients are followed daily for toxicity and blood count recovery. In addition to safety, neutrophil and platelet recovery and engraftment were investigated as efficacy end points. A total of 15 subjects have been treated; all have tolerated the procedure very well except for 1 patient who did not finish the last 10 min of therapy because of nausea thought to be secondary to a concomitant medication. In terms of efficacy, final data from the study indicate an encouraging median time to neutrophil recovery of 14 days compared to 20.5 in historic data (*n* = 48) and a median time to platelet count recovery of 37.5 compared to 38 in historic data (**Table 1**). HBO also resulted in improved day 100 survival (*p* = 0.051) and in improvement in the percentage of patients who demonstrated Neutrophil recovery was not significant platelet count recovery (*p* = 0.013). HBO also resulted in statistically significant reduction in median EPO level from baseline (−30.37 mU/

*Blood count recovery in umbilical cord blood transplantation pilot study utilizing hyperbaric oxygen (HBO).*

Neutrophil recovery (n/%) No 0% 6 (12%) NS

Platelet recovery (n/%) No 0% 15 (31%) 0.013

Median time to neutrophil recovery (range) 14 (6–45) 20.5 (571) NS Median time to platelet recovery (range) 37.5 (0–85) 38 (0–161) NS

**HBO (***n* **= 15)**

Yes 15 (100%) 42 (82%)

Yes 15 (100%) 33 (69%)

**Historic (***n* **= 48)** *p* **value**

In a follow-up study, the long-term outcome of patients in this pilot HBO study in UCB transplantation was examined. Patients' outcome was compared to a historic control group. The 6-month survival in the HBO group was 100%, compared to 67.0% in the control group (95% CI 50.1–79.4%, *p* < 0.0001) [38]. HBO-treated patients had on average lower relapse and non-relapse mortality rates, and less chronic graft-versus-host disease (GVHD), but had increased acute GVHD. However, these differences were not statistically significant, probably because of the small sample size. In the HBO-treated cohort, immune-reconstitution analysis showed significant improvement in early B-cell recovery, with a trend toward improvement in early NK cell recovery. The ratio of 8 hours to baseline EPO levels was examined. A nonsignificant trend toward lower EPO values was found in those who did not relapse or die in year 1 than those who did die or relapse. Disease progression-free survival was also improved in those who had more than 80% reduction in EPO levels in response to HBO. This study highlights the longterm safety of HBO therapy when used prior to UCB transplantation. It also shows a relationship between HBO-induced EPO reduction, early NK cell recovery and posttransplant disease progression. Since lower rates of relapse have been reported in association with higher early NK cell recovery [39], it was hypothesized that by reducing EPO, HBO improves early NK cell recovery, and improved NK cell recov-

*DOI: http://dx.doi.org/10.5772/intechopen.85223*


#### *Effect of Hyperbaric Oxygen on Hematopoietic Stem Cell Transplantation DOI: http://dx.doi.org/10.5772/intechopen.85223*

**Table 1.**

*Advances in Hematologic Malignancies*

cells enriches CD71<sup>+</sup>

summarized in the next three paragraphs.

**4.1 Details of HBO therapy**

every 30 min of HBO treatment.

**4.2 HBO in UCB transplantation**

UCB CD34+

RNA-seq for transcriptional assessment, investigators found that EPO treatment of

throid commitment (**Figure 4**). In the same data set, EPO treatment was associated with signal transducer and activator of transcription 3 (STAT3) pathway activation (**Figure 4**). Importantly, signal transducer and activator of transcription 3 (STAT3)

To date, two pilot clinical trials exploring HBO in UCB transplantation as well as autologous hematopoietic cell transplantation (HCT) have been completed. In both studies HBO was given in standard fashion at least 6 hours prior to HSCP infusion on day 0 of their transplant (**Figure 5**). The first aim of these studies is to examine the safety and tolerability of HBO in the setting of HCT. In addition, these studies explored the impact of HBO on blood count recovery as well as EPO levels posttransplant. Details of HBO therapy and the results of these studies are being

After receiving routine clinical care on day 0 (the day of HSPC infusion), subjects were exposed to HBO for a total of 90 min after compression to 2.5 atmosphere absolutes (ATA) in a monoplace hyperbaric chamber (Model 3200/3200R, Sechrist Industries, Inc., USA), breathing 100% oxygen. The subjects spent 10–15 min during the compression and decompression phases and 10 min room air breaks for

Based on the previously mentioned pre-clinical data, a pilot clinical trial investigating the safety of HBO in UCB transplant was initiated. Patients considered

*Clinical trial schema incorporating hyperbaric oxygen (HBO) into hematopoietic cell transplantation.*

is a known downstream effector of EPOR signal transduction [34–37].

**4. Pilot clinical data supporting HBO role in HSC transplantation**

early erythroid cells, consistent with early ery-

**156**

**Figure 5.**

*Blood count recovery in umbilical cord blood transplantation pilot study utilizing hyperbaric oxygen (HBO).*

for either standard myeloablative conditioning (MAC) (higher intensity chemotherapy and radiation) or standard reduced intensity conditioning (RIC) (lesser intensity chemotherapy and radiation) UCB transplantation were enrolled. In this study, HBO treatment was administered on day 0 of the transplant. The treatment consisted of exposure to 100% oxygen at 2.5 ATA for a total of 2 hours, in a single see-through hyperbaric chamber. Six hours from the start of HBO, single or double UCB units are infused, and patients are followed daily for toxicity and blood count recovery. In addition to safety, neutrophil and platelet recovery and engraftment were investigated as efficacy end points. A total of 15 subjects have been treated; all have tolerated the procedure very well except for 1 patient who did not finish the last 10 min of therapy because of nausea thought to be secondary to a concomitant medication. In terms of efficacy, final data from the study indicate an encouraging median time to neutrophil recovery of 14 days compared to 20.5 in historic data (*n* = 48) and a median time to platelet count recovery of 37.5 compared to 38 in historic data (**Table 1**). HBO also resulted in improved day 100 survival (*p* = 0.051) and in improvement in the percentage of patients who demonstrated Neutrophil recovery was not significant platelet count recovery (*p* = 0.013). HBO also resulted in statistically significant reduction in median EPO level from baseline (−30.37 mU/ ml+/−31.68, *p* = 0.004).

In a follow-up study, the long-term outcome of patients in this pilot HBO study in UCB transplantation was examined. Patients' outcome was compared to a historic control group. The 6-month survival in the HBO group was 100%, compared to 67.0% in the control group (95% CI 50.1–79.4%, *p* < 0.0001) [38]. HBO-treated patients had on average lower relapse and non-relapse mortality rates, and less chronic graft-versus-host disease (GVHD), but had increased acute GVHD. However, these differences were not statistically significant, probably because of the small sample size. In the HBO-treated cohort, immune-reconstitution analysis showed significant improvement in early B-cell recovery, with a trend toward improvement in early NK cell recovery. The ratio of 8 hours to baseline EPO levels was examined. A nonsignificant trend toward lower EPO values was found in those who did not relapse or die in year 1 than those who did die or relapse. Disease progression-free survival was also improved in those who had more than 80% reduction in EPO levels in response to HBO. This study highlights the longterm safety of HBO therapy when used prior to UCB transplantation. It also shows a relationship between HBO-induced EPO reduction, early NK cell recovery and posttransplant disease progression. Since lower rates of relapse have been reported in association with higher early NK cell recovery [39], it was hypothesized that by reducing EPO, HBO improves early NK cell recovery, and improved NK cell recovery slows down disease progression.

#### **4.3 HBO in autologous HCT**

Encouraged by the results of HBO in UCB transplantation, the same group conducted a pilot study in Auto-HSPC transplantation. A total of 20 patients were treated on the Auto-HSPC transplant study. HBO therapy was very well tolerated as 19 completed full therapy [40]. For efficacy comparison, HBO subjects were matched to historical controls from the same institution based on gender, age (within 5 years), disease type (multiple myeloma or lymphoma), and preparative regimen. The median time to neutrophil count recovery was 11 days in both cohorts, the HBO and control cohorts. However, time to neutrophil recovery was approximately 1 day sooner for HBO than historical controls taking into account the full distribution estimates of Kaplan-Meier estimator (log rank *p* = 0.005). The median time to platelet count recovery was 16 versus 18 days for the HBO and control cohorts, respectively (log rank *p* < 0.0001).

In a separate analysis, HBO effects on other outcomes of post-autologous transplantation were evaluated. In this analysis, the HBO cohort patients who completed HBO therapy (*n* = 19) were compared with historic patients (*n* = 225) [40]. The average days of GCSF use were 6 days in the HBO cohort compared to 8 days in controls (*p* < 0.01). Also, HBO patients had significantly less mucositis (26.3 versus 64.2%, *p* < 0.01).

#### **5. HBO and stem cell mobilization**

In the previous section, the effects of HBO on stem cell homing and engraftment posttransplant were reviewed. Interestingly, HBO can also help with stem cell/progenitor cell mobilization from the bone marrow [41]. However, the mobilized stem/ progenitor cells exhibited characteristics of endothelial progenitor cells [42].

#### **6. Current and future prospective**

Incorporating HBO into HCT backbone represents a new direction in the field of HCT aiming at improving the outcome of HCT by improving HSPC homing and subsequent engraftment. Accumulated data suggest improvement in immune reconstitution too. Targeting EPO at the time of HSPC infusion represents a new understanding of EPO role in basic HSCP functions, including cell differentiation, transmigration, homing, and engraftment. Though these studies represent an early attempt at understanding EPO role in HSCP biologic functions and HBO's role in blocking EPO/EPOR signaling in HCT transplantation, the accumulated data seem to be promising. Currently, a phase II study investigating HBO in Auto-HCT is open for enrollment (ClinicalTrials.gov Identifier: NCT03398200). Another phase II study investigating HBO in UCB transplantation is expected to be open for enrollment in early 2019 (ClinicalTrials.gov Identifier: NCT03739502). Both of these studies are randomized prospective clinical trials that focus on investigating HBO effects on time to neutrophil recovery, platelet count recovery, blood and platelet transfusion requirements, and growth factor use. Additionally, both studies will be evaluating disease response posttransplant. Immune reconstitution will be examined in an attempt to correlate that to disease response posttransplant, hypothesizing that HBOT improves immune reconstitution which in turn will result in improved disease response to transplant. Finally, these studies will examine HBO effects on EPO and IL-15 levels posttransplant. The study in UCB transplantation will also focus on time to achieving full-donor chimerism as that might influence

**159**

*Effect of Hyperbaric Oxygen on Hematopoietic Stem Cell Transplantation*

disease control posttransplant. This wave of phase II studies will be essential in establishing the efficacy of such procedure in HCT and might lead to future phase

to effectively block EPO/EPOR signaling during HCT. In a previous study, one single HBO treatment 6 hours prior to HSPC infusion was used. It was noticed that EPO level rebounds as early as 24 hours after HBO treatment [30]; accordingly additional HBO therapy might keep EPO levels low for 48 hours, which is the duration during which homing occurs. To accomplish that, investigators will have to treat the recipients 24 hours after HSPC infusion, which means the infused HSPCs

will be exposed to hyperbaric conditions. In their experience, direct CD34<sup>+</sup>

exposure to HBO reduced their proliferation, impaired their in vitro transmigration, and reduced their erythroid differentiation [43]. These effects were statistically significant, but the biological effects were minimal which in theory should

already homed to the bone marrow as these effects might help with HSPC retention

Finally, in addition to reducing EPO and affecting EPO/EPOR signaling, HBO might have additional effects beyond EPO/EPOR signaling that might impact HSPC

Targeting EPO using HBO in hematopoietic cell transplantation is a new direction in the HCT field which will potentially have major impact on the outcome of HCT. By improving HSPC homing, engraftment, and immune reconstitution, HBO therapy will have the potential to improve the outcome of HCT by improving patient recovery and by reducing posttransplant complications related to infections. Overall, that might reduce the cost of HCT. Though data from pre-clinical and pilot clinical studies are encouraging, data from current and future phase II studies might show more definitive data in support of this application. Also future studies will be needed to examine HBO effects on bone marrow microenviron-

cell behavior significantly. Additionally, these direct

cells are desirable when it comes to the HSPCs that have

An additional area for future investigation is defining the optimal HBO schedule

cell

*DOI: http://dx.doi.org/10.5772/intechopen.85223*

III studies.

not influence UCB CD34<sup>+</sup>

in the bone marrow.

biologic functions.

**7. Conclusions**

ment elements.

**Conflict of interest**

No conflict of interest to declare.

HBO effects on UCB CD34+

#### *Effect of Hyperbaric Oxygen on Hematopoietic Stem Cell Transplantation DOI: http://dx.doi.org/10.5772/intechopen.85223*

disease control posttransplant. This wave of phase II studies will be essential in establishing the efficacy of such procedure in HCT and might lead to future phase III studies.

An additional area for future investigation is defining the optimal HBO schedule to effectively block EPO/EPOR signaling during HCT. In a previous study, one single HBO treatment 6 hours prior to HSPC infusion was used. It was noticed that EPO level rebounds as early as 24 hours after HBO treatment [30]; accordingly additional HBO therapy might keep EPO levels low for 48 hours, which is the duration during which homing occurs. To accomplish that, investigators will have to treat the recipients 24 hours after HSPC infusion, which means the infused HSPCs will be exposed to hyperbaric conditions. In their experience, direct CD34<sup>+</sup> cell exposure to HBO reduced their proliferation, impaired their in vitro transmigration, and reduced their erythroid differentiation [43]. These effects were statistically significant, but the biological effects were minimal which in theory should not influence UCB CD34<sup>+</sup> cell behavior significantly. Additionally, these direct HBO effects on UCB CD34+ cells are desirable when it comes to the HSPCs that have already homed to the bone marrow as these effects might help with HSPC retention in the bone marrow.

Finally, in addition to reducing EPO and affecting EPO/EPOR signaling, HBO might have additional effects beyond EPO/EPOR signaling that might impact HSPC biologic functions.
