Alpha-1 Antitrypsin Augmentation Therapy in Chronic Pancreatitis Patients Undergoing Total Pancreatectomy and Islet Autotransplantation: A Randomized, Controlled Study

Abstract

Stress-induced islet graft loss during the peri-transplantation period reduces the efficacy of islet transplantation. In this prospective, randomized, double-blind clinical trial, we evaluated the safety and efficacy of 60 mg/kg human alpha-1 antitrypsin (AAT) or placebo infusion weekly for four doses beginning before surgery in chronic pancreatitis (CP) patients undergoing total pancreatectomy and islet autotransplantation (TP-IAT). Subjects were followed for 12 months post-TP-IAT. The dose of AAT was safe, as there was no difference in the types and severity of adverse events in participants from both groups. There were some biochemical signals of treatment effect with a higher oxygen consumption rate in AAT islets before transplantation and a lower serum C-peptide (an indicator of islet death) in the AAT group at 15 min after islet infusion. Findings per the statistical analysis plan using a modified intention to treat analysis showed no difference in the C-peptide area under the curve (AUC) following a mixed meal tolerance test at 12 months post-TP-IAT. There was no difference in the secondary and exploratory outcomes. Although AAT therapy did not show improvement in C-peptide AUC in this study, AAT therapy is safe in CP patients and there are experiences gained on optimal clinical trial design in this challenging disease.

Introduction

Chronic pancreatitis (CP) is a syndrome characterized by pancreatic inflammation, fibrosis, and scarring that results in exocrine and endocrine deficiency ¹ . Majority of CP patients also experience severe and unrelenting pain. The incidence of CP ranges from 5 to 12/100,000 with a prevalence of about 50/100,000 persons. When medical and surgical procedures fail, total pancreatectomy becomes an option to improve pain control and quality of life (QOL) ² . Total pancreatectomy alone causes type 3c diabetes, which is brittle. Total pancreatectomy and islet autotransplantation (TP-IAT) can reduce pain, improve QOL, and avoid type 3c diabetes if the islet transplantation is successful. However, poor post-transplant islet function caused by preoperative loss of pancreatic b-cell mass from long-term inflammation within the diseased pancreas and by stress-induced islet cell death during islet harvest and post-transplantation is a major issue associated with this procedure. Furthermore, isolated islets have significant ischemic time before autologous transplantation in the patient. As a result, early islet destruction and primary non-function after intraportal islet infusion leave more than 60% of patients requiring insulin ³ . Effective therapies that can reduce islet cell death and facilitate islet cell engraftment after transplantation are needed to increase the efficacy of this procedure.

Clinical trials using anti-inflammatory and other strategies have been conducted to improve the survival of autograft after transplantation ⁴ – ⁹ . Alpha-1 antitrypsin (AAT, also called alpha-1 proteinase inhibitor, A1PI) is a serine protease inhibitor that belongs to the serpin superfamily of proteins. AAT has a high concentration in blood, and AAT concentrates prepared from human plasma are approved for clinical use in AAT deficiency (AATD) as an affinity-purified human product ¹⁰ . AAT inhibits many proteases, including neutrophil elastase, cathepsin G, proteinase-3, thrombin, trypsin, and chymotrypsin ¹¹ . AAT products are licensed for intravenous administration at a dose of 60 mg/kg weekly to patients with AATD. In addition to the inhibition of proteases, AAT exerts non–protease-dependent anti-inflammatory effects via suppressing cytokine production, complement activation, and immune cell infiltration ¹² . AAT also functions as an anti-apoptotic factor for endothelial cells and vascular smooth muscle cells^13,14. AAT induces vascular endothelial growth factor (VEGF) expression and release, protects VEGF from proteolytic cleavage by elastase, promotes endothelial cell viability, and enhances islet graft survival ¹⁵ .

Recent studies indicate that AAT has beneficial effects in treating diabetes in rodents. AAT protects β cells from apoptosis induced by pro-inflammatory cytokines and streptozotocin ¹⁶ . A single injection of AAT to the non-obese diabetic (NOD) mice reduced the intensity of insulitis, increased β cell mass, promoted β cell regeneration, and prevented the onset of diabetes via modulating T regulatory cells ¹⁷ . AAT has been shown to protect islets from graft failure and immune rejection in mouse transplantation models with readily vascularized islet grafts^18,19. Adding AAT into ductal injection and collagenase solution improved porcine islet isolation by inhibiting trypsin activity during pancreatic digestion ²⁰ . AAT monotherapy prolongs islet allograft survival in mice by enhancing intra-islet VEGF expression and promoting islet revascularization ¹⁸ . AAT treatment improved the survival of islets after partial pancreatectomy and intrahepatic autologous islet transplantation in non-human primates ²¹ . The beneficial effects of AAT in the islet transplantation setting may be mediated by its anti-apoptotic and anti-inflammatory properties and/or promotion of islet revascularization.

AAT products have been used for treating emphysema for more than 25 years, with a remarkable safety record ²² . AAT therapy has also been tested in several clinical trials, including in lung inflammation, type 1 diabetes, acute graft versus host disease, organ injury in patients undergoing cardiac surgery, and other indications (www.clinicaltrials.gov). The safety, tolerability, and efficacy of intravenous infusion of AAT in patients with newly diagnosed type 1 diabetes have been documented^23–25.

AAT is an acute-phase reactant protein. As such, serum levels of AAT can increase markedly after stress. Whether augmented levels of AAT infused exogenously have benefits following human TP-IAT remains unknown. Data from rodent studies ¹⁹ suggest that AAT augmentation therapy may enhance islet survival after autotransplantation in CP models. Here, we evaluated the safety and efficacy of preoperative and postoperative AAT infusion in patients who undergo TP-IAT. Subjects who received saline at the same schedule were included as placebo controls. Adverse events (AEs), islet function, and QOL of participants were compared between the AAT and the placebo groups.

Materials and Methods

Study Design

A single-center, randomized, double-blind, placebo-controlled study was conducted following informed consent on CP subjects undergoing TP-IAT at the Medical University of South Carolina (MUSC) between January 2017 and November 2021. The study inclusion criteria included age ≥18 years with a planned TP-IAT surgery. Participants were diabetes-free before surgery as determined using the American Diabetes Association criteria for type 2 diabetes. The exclusion criteria included patients who were immunosuppressed, had previous Puestow or Frey pancreatic surgery, or had contraindications to AAT therapy [immunoglobulin A (IgA) deficiency, known antibodies against IgA, or individuals with a history of severe immediate hypersensitivity reactions, including anaphylaxis to A1PI products].

The study was intended to enroll 48 participants. Participants were randomized into 60 mg/kg intravenous AAT (Prolastin-C, A1PI, Grifols, Los Angeles, CA) or intravenous 0.9% saline placebo groups in a 2:1 ratio. The first AAT infusion started in the morning before the total pancreatectomy. Subsequent infusions were given at 7 ± 2, 14 ± 2, and 21 ± 2 days post-TP-IAT. Participants were asked to return for the mixed meal tolerance test (MMTT) at days 75 and 365 post-TP-IAT in addition to their routine post-operative visits at 1, 3, 6, and 9 months and then annually.

The primary outcome measure was serum C-peptide area under the curve (AUC) following a 4-h MMTT at 365 ± 14 days post-transplantation in the modified intent to treat population who received at least one dose of study drug infusion. Safety was continually evaluated throughout the study.

Written informed consent from each participant was obtained. An independent data safety monitoring board (DSMB) designated by the National Institute of Diabetes and Digestive and Kidney Diseases held regular safety reviews. The clinicaltrials.gov registration number is NCT02947087.

Total Pancreatectomy and Islet Autotransplantation

A total pancreatectomy was performed, leaving an infusion catheter in the umbilical/portal vein ²⁶ . The pancreas was transported aseptically to the MUSC Center for Cellular Therapy, a Good Manufacturing Practice facility, and evaluated for weight, fibrosis, and fat tissue infiltration. Each pancreas was given a fibrosis score from 0 to 10, with 10 as the most fibrotic. The pancreas was then perfused and digested with cold Liberase^TM with Thermolysin (Roche, Basel, Switzerland) to release islets. Non-purified total islet products were washed and resuspended in 5% human albumin supplemented with heparin (70 units/kg of body weight), put into an infusion bag, and infused into patient’s liver via the portal vein. Portal vein pressure was monitored during islet infusion as described previously^8,27.

Blood Glucose Control and Islet Function Measurement Post-TP-IAT

All TP-IAT patients were given insulin during the post-transplantation period to reduce the stress for newly transplanted islets. Insulin use after surgery was measured. Participants were weaned off insulin following normal blood glucose levels and hemoglobin A1c (HbA1c). Insulin use and diabetes status were recorded at each follow-up visit. Insulin independence was defined by not using any insulin but with normal HbA1c.

Serum AAT Concentration

Blood samples were collected at baseline (before AAT infusion and total pancreatectomy), before islet infusion, and 1 day after islet infusion for measurement of serum AAT levels using a human AAT ELISA kit (SERPINA1, Abcam, Cambridge, MA, USA), following the manufacturer’s instructions.

Oxygen Consumption Rate (OCR)

OCR was measured from a sample of 1,000–2,000 islet equivalent numbers using the MicroOxygen Update System FO/SYSZ-P175 (Instech Laboratories, Plymouth Meeting, PA, USA) as described previously ⁸ . Deoxyribonucleic acid (DNA) content in each sample was measured using the Quant-iT^TM PicoGreen^TM dsDNA Assay kit (Molecular Probes, Eugen, OR, USA). Fluorescence density was measured by a Synergy HT microplate reader (BioTek, Winooski, VT, USA). OCR/DNA (nmol O₂/min·mg DNA) values were compared between AAT and placebo subjects.

Mixed Meal Tolerance Test

During the MMTT, subjects fasted overnight and were asked to drink 6 ml/kg of BOOST, which contains a mixture of protein, fat, and carbohydrates. Participants’ blood was drawn at 0, 15, 30, 60, 90, 120, 180, and 240 min and C-peptide levels at each time point were measured using ELISA (Human STELLUX® Chemiluminescent Human C-peptide ELISA kit, APLCO Diagnostics, Salem, NH) as described previously ⁸ . The AUC of the C-peptide levels was calculated following the trapezoidal rule.

Short Form-12 (SF-12) QOL Scores

The SF-12 was recorded from all participants at baseline and with return clinic visits at 3, 6, and 12 months.

Statistical Analyses

Differences between the two treatment groups were compared by two-tailed independent sample t-tests. Serum human AAT concentration and human C-peptide were compared by two-way analysis of variance with Tukey correction. Missing data were not imputed. All values are presented as mean and standard error unless otherwise specified. A P-value < 0.05 was denoted as statistically significant.

Results

Baseline Characterization

Among the 48 subjects who signed consent, 5 did not receive TP-IAT or the allocated study drug. Therefore, baseline data from 14 subjects in the placebo group were compared to 29 subjects in the AAT group. Characteristics of the study participants are summarized in Table 1. There were no significant differences in baseline characteristics related to age, body weight, body mass index, or HbA1c levels. Control participants had a longer duration of CP compared to AAT participants (10.3 ± 5.2 vs 6.4 ± 5.5 years, P = 0.03, Table 1). AAT pancreases trended toward a higher fibrosis score than controls (Fig. 1A), but the difference was not statistically significant. OCR indexed to DNA, a suggested prospective positive quality indicator of clinical islet preparation ²⁸ , trended higher in the islets from the AAT group (Fig. 1B). There were no significant differences in the total volume of islet product, islet equivalent (IEQ) infused, as measured by IEQ/kg of body weight. Mean portal vein pressures during and post-infusion were higher in the AAT group, although pressures from both groups were within the acceptable range (Table 1).

Table 1.

Baseline Characteristics.

Characteristics	Average of control subjects (n = 14)		Average of AAT subjects (n = 29)		P
	Mean	SE	Mean	SE
Age (years)	38.29	13.21	39.31	12.26	0.76
Body weight (kg)	73.79	26.77	78.07	21.49	0.61
BMI (kg/m2)	24.31	6.82	27.96	6.28	0.25
HbA1C pre-operative (%)	5.43	0.29	5.42	0.84	0.99
Years of CP	10.29	5.18	6.36	5.45	0.03
Total volume	250.21	34.2	389.17	40.9	0.81
Total islets infused IEQ	258,604	72,847	339,077	50,122	0.33
IEQ/kg	3,325	655	4,329	537	0.19
Hepatic pressure (mmHg)
Pre-infusion	6.86	2.93	8.07	4.09	0.27
During infusion	9.21	4.51	13.51	7.74	0.027
Post-infusion	10.43	4.96	17	8.49	0.003

BMI: body mass index; HbA1c: hemoglobin A1c; IEQ: islet equivalent; SE: standard error; AAT: alpha-1 antitrypsin; CP: chronic pancreatitis.

Figure 1.

Fibrosis score of the pancreas, OCR, serum human AAT, and C-peptide levels in placebo (n = 14) and AAT participants (n = 29). (A). Fibrosis score of the pancreas, with 10 having the most and 0 having the least fibrosis. (B) OCR/DNA levels in islets harvested from the placebo and the AAT participants. Each dot represents one subject. (C). Human AAT levels in the placebo or the AAT participants before surgery (D0_S), before islet transplantation (D0_SA), and 24 h after islet transplantation (D1_S). (D). Human serum C-peptide levels in participants before total pancreatectomy (D0), before islet transplantation (D0_0), 15 min after initiation of islet transplantation (D0_15m), 3 h after initiation of islet transplantation (D0_3h), and 7 days post-TP-IAT. Each dot represents a participant. OCR: oxygen consumption rate; AAT: alpha-1 antitrypsin; DNA: deoxyribonucleic acid; TP-IAT: total pancreatectomy and islet autotransplantation. P-values are denoted as follows: *P < 0.05; **P < 0.01; ****P < 0.0001 (two-way ANOVA).

Serum AAT Concentrations and C-Peptide Levels After Islet Infusion

AAT concentration in the serum of participants at baseline, before islet transplantation (about 7–8 h after the first AAT infusion), and day 1 post-infusion is shown in Fig. 1C. In the AAT group, there was a significant increase in human AAT levels before islet infusion compared to baseline, but the level fell to a lower level by day 1 (Fig. 1C). Serum C-peptide, an index of islet injury at early time points after islet infusion ²⁹ , was significantly lower in the AAT group at 15 min after islet infusion compared to placebo, although the levels were comparable 3 h after islet infusion (Fig. 1D).

AEs and Serious Adverse Events (SAEs)

AEs and SAEs were recorded throughout the study, and their severity and relationship to the treatment were evaluated. There were 19 AEs observed in 15 AAT subjects (51.7%) and 10 AEs observed in 6 placebo subjects (42.9%). Among the AEs, abdominal pain, fatigue, nausea and vomiting, hypotension, and cellulitis were observed in subjects from both treatment groups (Table 2).

Table 2.

Non-serious AEs.

AEs	AAT (n = 29)	Placebo (n = 14)	Total study population (n = 43)
Total AEs	15/29 (51.72%)	6/14 (42.86%)	21/43 (48.84%)
Specific types of AEs
Abdominal pain	3/29 (10.34%)	3/14 (21.43%)	6/43 (13.95%)
Fatigue	2/29 (6.9%)	0/14 (0%)	2/43 (4.65%)
Nausea and vomiting	1/29 (3.45%)	1/14 (7.14%)	2/43 (4.65%)
Hypotension	3/29 (10.34%)	1/14 (7.14%)	4/43 (9.30%)
Cellulitis	1/29 (3.45%)	1/14 (7.14%)	2/43 (4.65%)
Urticaria	0/29 (0%)	1/14 (7.14%)	1/43 (2.33%)
Hyperglycemia	0/29 (0%)	1/14 (7.14%)	1/43 (2.33%)
Anemia	1/29 (3.45%)	1/14 (7.14%)	2/43 (4.65%)
Portal vein thrombosis	1/29 (3.45%)	1/14 (7.14%)	2/43 (4.65%)
Urinary tract infection	1/29 (3.45%)	0/14 (0%)	1/43 (2.33%)
Seizure	1/29 (3.45%)	0/14 (0%)	1/43 (2.33%)
Gastritis	1/29 (3.45%)	0/14 (0%)	1/43 (2.33%)
Diarrhea	1/29 (3.45%)	0/14 (0%)	1/43 (2.33%)
Acute kidney injury	1/29 (3.45%)	0/14 (0%)	1/43 (2.33%)
Wound seroma	1/29 (3.45%)	0/14 (0%)	1/43 (2.33%)
Headache	1/29 (3.45%)	0/14 (0%)	1/43 (2.33%)

AE: adverse event; AAT: alpha-1 antitrypsin.

SAEs occurred in 69.8% of participants, including 34 SAEs in 22 AAT subjects (75.9%) and 13 SAEs in 8 placebo subjects (57.1%). SAEs occur most often from gastrointestinal manifestations, including worsened abdominal pain, nausea and vomiting, gastric ulcer, colitis, and abdominal fluid collections (Table 2). Portal vein thrombosis was detected in four participants, two each in the AAT and the placebo arms and one event in each arm was characterized as a SAE (Table 3).

Table 3.

Serious Adverse Events (SAEs).

SAEs	AAT (n = 29)	Placebo (n = 14)	Total study population (n = 43)
Total serious adverse events	22/29 (75.86%)	8/14 (57.14%)	30/43 (69.77%)
Specific types of serious adverse events
Abdominal pain	10/29 (34.48%)	4/14 (28.57%)	14/43 (32.56%)
Nausea and vomiting	3/29 (10.34%)	2/14 (14.29%)	5/43 (11.63%)
Gastric ulcer (with or without bleeding)	6/29 (20.69%)	1/14 (7.14%)	7/43 (16.28%)
Colitis	3/29 (10.34%)	1/14 (7.14%)	4/43 (9.30%)
Abdominal fluid collection	3/29 (10.34%)	2/14 (14.29%)	5/43 (11.63%)
Hyperglycemia	2/29 (6.90%)	2/14 (14.29%)	4/43 (9.30%)
Portal vein thrombosis	1/29 (3.45%)	1/14 (7.14%)	2/43 (4.65%)
Pulmonary embolism	1/29 (3.45%)	0/14 (0%)	1/43 (2.33%)
Septic shock	1/29 (3.45%)	0/14 (0%)	1/43 (2.33%)
GI bleeding	1/29 (3.45%)	0/14 (0%)	1/43 (2.33%)
Death	2/29 (6.90%)	0/14 (0%)	2/43 (4.65%)

AAT: alpha-1 antitrypsin; GI: gastrointestinal.

There were two deaths in the subjects assigned to the AAT group. Both subjects received only the first two doses of AAT, with death occurring in both at approximately 3 months after the last AAT infusion. The cause of death of one subject was due to bleeding in the pancreatectomy bed. The cause of death of the other subject was unknown but occurred at home. Since both deaths occurred long after the last AAT injection, both were deemed not related to AAT infusion. All the AEs and SAEs have been observed in historical TP-IAT subjects and none was determined related to AAT infusion by the DSMB.

Islet Function Post-TP-IAT

The primary efficacy endpoint of this study, islet graft function as measured by the MMTT at 12 months post-transplantation, was not significantly different between groups. Among those who returned for testing, C-peptide AUC at 3 months was 543.8 ± 93.0 ng/ml × min in placebo versus 422.6 ± 54.0 ng/ml × min in the AAT group (P = 0.33). The C-peptide AUC at 12 months was 354.1 ± 78.0 ng/ml × min in placebo versus 232.5 ± 42.2 ng/ml × min in AAT group (P = 0.43). The C-peptide AUC/IEQ/kg at 3 months was 0.11 ± 0.02 ng/ml × min in placebo versus 0.13 ± 0.01 ng/ml × min in the AAT group (P = 0.32). The C-peptide AUC/IEQ/kg at 12 months was 0.09 ± 0.01 ng/ml × min/IEQ/kg in placebo versus 0.10 ± 0.05 ng/ml × min/IEQ/kg in AAT group (P = 0.1).

At 3 months, 7/14 (50%) in the placebo group and 22/29 (76%) in the AAT group returned for the MMTT test. At 12-month post-TP-IAT, 10/14 (71%) in the placebo group and 18/29 (62%) in the AAT group returned for the MMTT test. Control participants used slightly more daily insulin on average at both 3 months (24.6 ± 5.0 vs 21.4 ± 4.6 units, P = 0.34, placebo vs AAT) and 12 months (26 ± 7.2 vs 20.3 ± 4.03 units, P = 0.48, placebo vs AAT). The insulin independence rate was 1/7 (14%) in placebo-treated and 4/18 (22%) in AAT-treated subjects at 6 months and 2/8 (25%) in placebo-treated and 3/17 (17.6%) in AAT-treated subjects at 12 months.

QOL of Participants

Among subjects who returned for testing from both groups, the SF-12 physiological QOL (pQOL) score improved in both groups. In the placebo patients, pQOL increased from 27.6 ± 9.0 pre-operative to 30.5 ± 12.4 at 6 months and to 33.6 ± 11.4 at 12 months (Fig. 2A). In the AAT subjects, pQOL improved from 23.3 ± 7.1 pre-operative to 31.8 ± 11.2 at 6 months and to 32.2 ± 12.6 at 12 months (Fig. 2A). The SF-12 psychological quality of life (PsQOL) score in placebo group was 39.6 ± 13.8 at pre-operative, compared to 31.4 ± 11.4 at 6 months and 37.7 ± 19.4 at 12 months (Fig. 2B). In AAT participants, the values trended higher from 35.7 ± 16.3 at pre-operative to 41.1 ± 12.1 at 6 months and 42.6 ± 12.4 at 12 months in the participants who returned (Fig. 2B). Comparatively, there was a trend of a better improvement of PsQOL at 6 months post-TP-IAT in the AAT group, although the difference was not statistically significant.

Figure 2.

SF-12 QOL in placebo and AAT subjects at Pre-op, M6, and M12. Averages of (A) physical QOL and (B) psychological QOL in the placebo and AAT subjects. Each dot represents one patient. Statistical analysis showed no difference between placebo and AAT participants by two-tailed independent sample t-tests. SF-12: Short Form-12; QOL: quality of life; AAT: alpha-1 antitrypsin; TP-IAT: total pancreatectomy and islet autotransplantation; Pre-op: before TP-IAT; M6: months post-TP-IAT;; M12: 12 months post-TP-IAT.

Discussion

Because AAT augmentation therapy promoted syngeneic and allogeneic islet survival after transplantation in murine models^12,30, we conducted this clinical trial to evaluate the safety and efficacy of AAT therapy in preserving islet survival and function in CP patients undergoing TP-IAT. We enrolled 48 participants from 2017 to 2021 and observed that AAT therapy is safe in this patient population, since all AEs observed have been seen in historical patients and were deemed not related to the treatment. AAT therapy seems to increase the islet quality based on a higher OCR value and the reduced immediate β cell death post-transplantation based on the C-peptide release. Although we did not observe significant improvement in insulin independence long term in our participants compared to those receiving a placebo, AAT participants used slightly less daily insulin on average at both 3 and 12 months. There was a trend of a better improvement of QOL at 6 months post-TP-IAT in the AAT group, although AAT therapy did not show improvement in C-peptide AUC.

The first and only human regulatory approval for AAT (A1PI) is in patients with severe AATD and emphysema. The dosing of AAT was empirically derived from the licensure of 60 mg/kg weekly, but in AAT-replete individuals these doses generate trough serum levels that are only slightly higher than baseline. These dosing guidelines and the modest impact seen in emphysema treatment trials have renewed calls for higher dose administration to optimize treatment efficacy.

Similarly, the optimal AAT dose to neutralize acute inflammation following a total pancreatectomy still needs to be defined ³¹ . The dose of weekly AAT injection at 60 mg/kg only led to increase in serum AAT level for a short period of time. We have shown in our animal study in which human islets were transplanted to the Nonobese diabetic/severe combined immunodeficiency (NOD-SCID) mice that a dose of 4 mg/ml of AAT was needed to achieve protective effects to transplanted islets via suppression of the instant blood-mediated immune reaction and/or macrophage activation^5,7. This dose corresponds to about 160 mg/kg in humans based on body weight every 2 days. Although an AAT dose of 240 mg/kg was confirmed to be safe in animals^32,33 and patients ³⁴ , a lower dose and more traditional dosing interval in this acute inflammatory condition proved ineffective^19,35. A recently published trial with an AAT dose of 90 mg/kg similar to this study also did not have efficacy improvements ⁴ . Therefore, very much higher doses of AAT before surgery would be needed to try and overcome the acute neutrophilic effects following pancreatic resection.

We observed significantly increased islet OCR/DNA level, a quality indicator positively related to islet function in vivo ³⁶ , from AAT subjects compared to placebo controls, suggesting a possible reduction of islet cell death in the AAT-treated recipients. This is consistent with the data from mouse studies that treatment with AAT may enhance islet viability/quality ¹² . Some survival advantages of AAT islets were also supported by reduced serum C-peptide levels right after islet transplantation, as increased C-peptide release was suggested as an indicator of islet cell death post-transplantation ²⁹ . It was possible that the benefit did not lead to more profound protection as the level of AAT dropped to the normal range within a couple of days.

This AAT study gave the first infusion on the day of the transplantation and many participants stayed in the hospital until the second dose on day 7. However, there were some missed infusion visits on days 14 and 21, likely because of travel issues over long distances with a tender abdomen. In addition, despite intensive efforts to get participants to return for the M12 test, only 71% of control and 62% of AAT participants returned for their visits. This population with chronic pain proved to be a difficult clinical trial population that will require creative approaches in future trials. In retrospect, telemedicine and home nursing visits may have ensured more patients achieved study follow-up.

There are some observations that have emerged from this clinical trial experience. Pressure from payers to discharge the post-operative patient sooner than historical norms ¹⁹ is ongoing. As such, optimal diabetes care is not usually achieved at the time of hospital discharge. Since glycemic control can affect islet function post-TP-IAT, a team approach to early outpatient transition is increasingly needed.

There are some limitations to our study. Most importantly, the follow-up at the time of primary efficacy analysis at 12 months was not complete, although we had attempted to use surrogates for the MMTT C-peptide AUC such as insulin dose reported by telephone. Not all individuals received all four doses of medication. Best attempts to capture AEs by telephone for the individuals who did not come for study visits may have missed some clinical outcomes.

Despite the lack of dramatic benefit from AAT, we demonstrated our ability as a single center to enroll CP patients for such a complex trial. The enrollment of 48 participants within 3 years suggests the willingness of this patient population to participate in research. This study researched a potentially novel approach to improve the efficacy of TP-IAT. We demonstrated the feasibility of enrolling and randomizing study subjects and obtained preliminary estimates of its success by comparing outcomes between the two treatment arms. The data gathered in this study provide essential information that can be utilized to design a larger multicenter clinical trial.

In conclusion, although we achieved the enrollment goal and demonstrated safety using AAT therapy, this single-center, randomized clinical trial showed minimal improvement of islet function post-TP-IAT. Although the current dose of AAT was safe and well tolerated in this patient population, this treatment regimen is not recommended, and a different treatment strategy is needed to improve the outcomes of TP-IAT.