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Over 80% of malaria-attributable deaths are in children under five. However, the only malaria vaccine recommended by the World Health Organization (WHO) for paediatric use, Mosquirix™, has limited efficacy. Complementary strategies, like monoclonal antibodies (mAbs), will be required to eradicate malaria. To discover new anti-malaria mAbs, we evaluated >28,000 antibody sequences from circulating B cells obtained from 45 Mosquirix™ vaccinees and selected 369 for testing. Many antibodies bound the circumsporozoite protein (CSP), a main surface protein on malaria and the malaria antigen in Mosquirix™, and several were exceptionally protective in mouse models of malaria. Through this work, we identified surprising correlations that suggest certain CSP sequences in Mosquirix™ may induce immunodominant antibody responses that dilute protective immunity. Further, we selected the antibodies most protective in preclinical mouse models and engineered them for improved manufacturability and developability to meet WHO guidelines. An optimised clinical candidate, MAM01, suitable for paediatric populations living in low-to-middle-income countries, was selected for clinical development.

Immunotherapy approaches focusing on T cells have provided breakthroughs in treating solid tumors. However, there remains an opportunity to drive anticancer immune responses via other cell types, particularly myeloid cells. ATRC-101 was identified via a target-agnostic process evaluating antibodies produced by the plasmablast population of B cells in a patient with non-small cell lung cancer experiencing an antitumor immune response during treatment with checkpoint inhibitor therapy. Here, we describe the target, antitumor activity in preclinical models, and data supporting a mechanism of action of ATRC-101. Immunohistochemistry studies demonstrated tumor-selective binding of ATRC-101 to multiple nonautologous tumor tissues. In biochemical analyses, ATRC-101 appears to target an extracellular, tumor-specific ribonucleoprotein (RNP) complex. In syngeneic murine models, ATRC-101 demonstrated robust antitumor activity and evidence of immune memory following rechallenge of cured mice with fresh tumor cells. ATRC-101 increased the relative abundance of conventional dendritic cell (cDC) type 1 cells in the blood within 24 h of dosing, increased CD8+ T cells and natural killer cells in blood and tumor over time, decreased cDC type 2 cells in the blood, and decreased monocytic myeloid-derived suppressor cells in the tumor. Cellular stress, including that induced by chemotherapy, increased the amount of ATRC-101 target in tumor cells, and ATRC-101 combined with doxorubicin enhanced efficacy compared with either agent alone. Taken together, these data demonstrate that ATRC-101 drives tumor destruction in preclinical models by targeting a tumor-specific RNP complex leading to activation of innate and adaptive immune responses.