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4553 Results from an Expanded Access Program of Anti-CD3/CD7 Immunotoxin Combination (T-Guard®) for the Treatment of Steroid-Refractory Acute Gvhd

Program: Oral and Poster Abstracts
Session: 722. Clinical Allogeneic Transplantation: Acute and Chronic GVHD, Immune Reconstitution: Poster III
Hematology Disease Topics & Pathways:
Diseases, Biological, antibodies, Therapies, GVHD, Immune Disorders, Clinically relevant, immune mechanism
Monday, December 9, 2019, 6:00 PM-8:00 PM
Hall B, Level 2 (Orange County Convention Center)

Lenneke F J Groningen1*, Christoph Groth, MD2*, Manita E J Bremmers3*, Eric G Hooren, MSc4*, Ypke V J M van Oosterhout4*, Nicole M A Blijlevens1, Matthias Stelljes5* and Walter J F M Van Der Velden, MD, PhD1

1Department of Hematology, Radboud University Medical Center, Nijmegen, Netherlands
2Dept. of Internal Medicine A, University Hospital of Muenster, Muenster, Germany
3Radboud University Medical Center, Nijmegen, Netherlands
4Xenikos BV, Nijmegen, Netherlands
5University Hospital of Muenster, Muenster, Germany

Background

More effective therapies for treating steroid-refractory acute GVHD (SR-aGVHD) are urgently needed. In our recent phase I/II study, we showed that anti-CD3/anti-CD7 immunotoxin (IT) therapy T-Guard was both safe and well tolerated, and yielded both a high rate of CR and high 6-month OS in high-risk patients (Groth et al. BBMT 2019). Following this study, patients with SR-aGVHD were offered T-Guard via an expanded access treatment program (EAP).

Objectives

We evaluated patients’ outcome after receiving T-Guard for SR-aGVHD. In addition, we examined the relationship between plasma citrulline levels (a biomarker of enterocyte mass) and the response to T-Guard in a subset of patients with SR-aGVHD of the gut, combining 16 patients from the phase I/II trial and 9 patients in the EAP group.

Methods

An EAP was started after completion of the phase I/II trial. This program was approved by the local ethics committee and the Health and Youth Care Inspectorate of the Dutch government. Adult patients with grade II-IV SR-aGVHD were eligible to receive T-Guard as their second- or third-line treatment for aGVHD. Patients with an uncontrolled infection, signs of moderate-severe chronic GVHD, and/or severe renal impairment were not eligible to receive T-Guard. Eligible patients received four 4-hour i.v. infusions of 4 mg/m2 T-Guard delivered at 48-hour intervals. In addition, plasma citrulline levels were measured at baseline and every 7 days after the start of T-Guard therapy using HPLC with mass spectrometry. A plasma citrulline level <10 µmol/L was considered to indicate severe GI-GVHD.

Results

From Jan. 2017 through Dec. 2018, 12 patients (8 male, 4 female; median age: 54 yr, range: 20-70 yr) who had received an allogeneic stem cell transplantation for myeloid or lymphoid malignancy were treated with T-Guard. T-Guard was given as the second-line therapy to 10 patients; the remaining 2 patients received T-Guard as the third-line therapy after receiving ruxolitinib (N=1) or cyclosporin-UVB (N=1). The median time between aGVHD onset and the start of T-Guard therapy was 7 days (range: 3-55 days).

SR-aGVHD was classified as grade II, III, or IV in 1, 7, and 4 patients, respectively. Nine patients (75%) had GI involvement, and the skin and liver were involved in 6 and 2 cases, respectively. All 12 patients were classified as high-risk in accordance with MacMillan et al. (BJH 2012), and the median albumin level at baseline was 23 g/L (range: 13-32 g/L).

By treatment day 28, 9 patients (75%) had achieved a clinical response, with 5 achieving complete remission. After a median follow-up of 16 months, 7 patients were alive; the 6-month and 1-year OS rate was 75% and 58%, respectively, which was significantly higher than historical controls; Figure 1. The cause of death in the other five patients was refractory aGVHD (N=3), relapse AML (N=1), and GVHD after undergoing a second stem cell transplantation for relapse AML (N=1).

No significant infusion-related reactions were recorded. As expected, the overall rate of infection was high, but was comparable to other cohorts; 1 and 2 patients developed an EBV or CMV infection, respectively, but these were manageable. The most common potentially treatment-related adverse events were transient worsening of hypoalbuminemia and thrombocytopenia. One patient developed grade 2 vascular leak syndrome, but this was easily managed. One patient developed severe thrombotic microangiopathy with renal insufficiency, but several contributing factors other than the use of T-Guard were present in this patient, including calcineurin toxicity, severe GI-GVHD, and CMV disease.

Our preliminary analysis of citrulline levels in 16 patients with GI-GVHD showed that mean baseline levels were extremely low (4.3 µmol/L; range: 2.9-17.9 µmol/L); 28 days after the start of T-guard, citrulline levels had increased significantly in the 9 patients who achieved complete remission; Figure 2.

Conclusion

Consistent with our recent phase I/II trial, our expanded access program in which 12 patients with high-risk SR-aGVHD received T-guard confirms that this treatment is safe and significantly improves patient outcome. A multicenter phase III study is planned to start in 2019 (BMT-CTN 1802).

Disclosures: Hooren: Xenikos BV: Employment. van Oosterhout: Xenikos BV: Employment.

*signifies non-member of ASH