First-in-human, randomized, double-blind, placebo-controlled, dose escalation trial of the anti-herpes simplex virus monoclonal antibody HDIT101 in healthy volunteers.

HDIT101 is a first-in-class humanized monoclonal antibody recognizing a conserved epitope in glycoprotein B, a target present on the surface of herpes simplex virus 1 (HSV-1) and HSV-2 particles as well as on virus-infected cells. This was a first-in-human, single-center, double-blind, placebo-controlled trial in 24 healthy volunteers, randomized 3:1 (placebo:active) in each of the six dose levels with escalating doses up to 12,150 mg HDIT101. HDIT101 was administered intravenously, to study safety, pharmacokinetics (PKs), and immunogenicity. HDIT101 was well-tolerated in all recipients and no serious or severe adverse events, no infusion-related reactions, and no events suggestive of dose limiting off-target toxicity occurred. The mean serum exposure (area under the curve from zero to infinity [AUC0-∞ ]) of HDIT101 showed a linear increase from 4340 h*µg/ml at a dose of 50 mg to 1,122,247 h*µg/ml at a dose of 12,150 mg. No immunogenic effects following HDIT101 exposure were observed at any of the applied doses. HDIT101 demonstrated the expected PK properties of a monoclonal antibody was well-tolerated, and could be safely administered even at excessively high doses that may be required for treatment of patients with septical HSV spread.

Preclinical evaluation of a diabody-based (177)Lu-radioimmunoconjugate for CD22-directed radioimmunotherapy in a non-Hodgkin lymphoma mouse model.

Radioimmunotherapy is considered as treatment option in recurrent and/or refractory B-cell non-Hodgkin lymphoma (B-NHL). To overcome the dose limiting bone marrow toxicity of IgG-based radioimmunoconjugates (RICs), we modified a humanized diabody with 5-, 10-, or 20-kDa polyethylene glycol (PEG) for CD22-targeted radioimmunotherapy using the low-energy ß-emitter lutetium-177 ((177)Lu). A favorable pharmacokinetic profile was observed for the 10-kDa-PEG-diabody in nude mice being xenografted with subcutaneous human Burkitt lymphoma. Even at high doses of 16 MBq this diabody RIC was well tolerated by NOD Rag1(null) IL2rγ(null) (NRG) mice and did not reveal signs of organ long-term toxicity 80 days post injection. Combination therapy of the diabody RIC with unconjugated anti-CD20 Rituximab demonstrated therapeutic efficacy in established disseminated mantle cell lymphoma xenograft models. When compared with the combination of the IgG formatted (177)Lu anti-CD22 antibody and Rituximab, dual targeted therapy with the diabody RIC achieved an improved reduction of disease burden in the first nine days following treatment. The data indicate that the PEGylated anti-CD22 diabody may have potential for extending the repertoire of radiopharmaceuticals for the treatment of patients with B-NHL.

A Humanized Anti-CD22-Onconase Antibody-Drug Conjugate Mediates Highly Potent Destruction of Targeted Tumor Cells.

Antibody-drug conjugates (ADCs) have evolved as a new class of potent cancer therapeutics. We here report on the development of ADCs with specificity for the B-cell lineage specific (surface) antigen CD22 being expressed in the majority of hematological malignancies. As targeting moiety a previously generated humanized anti-CD22 single-chain variable fragment (scFv) derivative from the monoclonal antibody RFB4 was reengineered into a humanized IgG1 antibody format (huRFB4). Onconase (ranpirnase), a clinically active pancreatic-type ribonuclease, was employed as cytotoxic payload moiety. Chemical conjugation via thiol-cleavable disulfide linkage retained full enzymatic activity and full binding affinity of the ADC. Development of sophisticated purification procedures using size exclusion and ion exchange chromatography allowed the separation of immunoconjugate species with stoichiometrically defined number of Onconase cargos. A minimum of two Onconase molecules per IgG was required for achieving significant in vitro cytotoxicity towards lymphoma and leukemia cell lines. Antibody-drug conjugates with an Onconase to antibody ratio of 3 : 1 exhibited an IC50 of 0.08 nM, corresponding to more than 18,400-fold increased cytotoxicity of the ADC when compared with unconjugated Onconase. These results justify further development of this ADC as a promising first-in-class compound for the treatment of CD22-positive malignancies.

High-level production of a humanized immunoRNase fusion protein from stably transfected myeloma cells.

ImmunoRNases represent a highly attractive alternative to conventional immunotoxins for cancer therapy. Quantitative production of immunoRNases in appropriate expression systems, however, remains a major challenge for further clinical development of these novel compounds. Here we describe a method for high-level production and purification of a fully functional immunoRNase fusion protein from supernatants of stably transfected mammalian cells.