GT Biopharma, Inc. announced the continuation of enrollment with patient 8 in its GTB-3550 clinical trial following the conclusion of a 30-day Covid-19 related pause in enrolling patients in all clinical trials currently being conducted at the University of Minnesota'sMasonic Cancer Center. Patients with CD33+ malignancies (primary induction failure or relapsed AML with failure of one reinduction attempt or high-risk MDS progressed on two lines of therapy) age 18 and older are eligible to participate in the GTB-3550 TriKE™ clinical trial (NCT03214666). The primary endpoint of the Study is to identify the maximum tolerated dose (MTD) of GTB-3550 TriKE. Correlative objectives include the number, phenotype, activation status and function of NK cells and T cells. The GTB-3550 TriKE clinical trial commenced patient enrollment in February 2020 for the treatment of relapsed/refractory acute myeloid leukemia (AML) and high-risk myelodysplastic syndrome (HR-MDS). To date, seven patients have been enrolled in the clinical trial; two patients treated at 5 mcg/kg/day, two patients treated at 10 mcg/kg/day, two patients at 25 mcg/kg/day, and one patient treated at 50 mcg/kg/day. All seven patients have completed therapy. The results to date have been positive and the company continues to expand the enrollment. High-risk myelodysplastic syndromes (HR-MDS) patient had failed hypomethylating agent and Luspatercept therapies prior to being treated with GTB-3550 at 50mcg/kg/day (three consecutive 96-hour continuous infusions). The patient achieved bone marrow blast level reduction from 12% before GTB-3550 therapy to 4.6% post GTB-3550 therapy determined by morphological assessment (61.7% reduction in cancer cells), and had stable hematologic parameters including normal platelet counts throughout therapy. Following this single course of GTB-3550 therapy and the significant reduction in bone marrow blast levels, the patient demonstrated clinical benefit from GTB-3550 therapy, and qualified for and has received a hematopoietic stem cell transplant (HSCT). The only treatment with curative intent for a majority of elderly HR-MDS or relapsed/refractory AML patients is allogeneic hematopoietic stem cell transplant (HSCT). GTB-3550 TriKE therapy represents a novel, low intensity therapeutic option which has the potential to increase HSCT eligibility for elderly HR-MDS and relapsed/refractory AML patients. Two patients with relapsed/refractory acute myeloid leukemia who has previously failed prior therapies prior to being treated with GTB-3550; one patient treated at 5mcg/kg/day achieved stable disease and another patient treated at 25mcg/kg/day experienced a 33% reduction in bone marrow blast levels. No signs of clinical immune activation, and no dose limiting toxicity such as cytokine release syndrome (CRS) or serious adverse events (SAEs) or fevers, tachycardia or constitutional symptoms have been observed in any patient treated to date with GTB-3550 TriKE. Correlative studies also showed no shedding of CD16 from patient's NK cells, and potent NK cell activation, proliferation and target cell killing without the need for supplemental autologous NK cell therapy. Targeted delivery of IL-15 to NK cells via GTB-3550 TriKE therapy showed preferential proliferation of NK cells, significantly less effect on CD8+ T-cells, and no observed toxicity at 25x the previous reported MTD for continuous infusion of recombinant human IL-15. GTB-3550 TriKE is a single-chain, tri-specific scFv.recombinant fusion protein conjugate composed of the variable regions of the heavy and light chains of anti-CD16 and anti-CD33 antibodies.