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Background Patients (pts) with RM SCCHN progressing after platinum have a median overall survival (OS) of 7-8 months with nivolumab or pembrolizumab. No other drug has shown meaningful activity in this setting. HLA-E is a non-classical MHC molecule that is highly expressed in 70% of SCCHN. By binding to the NKG2A receptor expressed on NK cells and T-lymphocytes, HLA-E inhibits their cytotoxic function. Monalizumab (mona) is a human IgG4 antibody targeting the NKG2A receptor. Methods The UPSTREAM trial is a biomarker-driven umbrella trial of several targeted therapies and immunotherapy for RM SCCHN (post platinum, ECOG 0-1, measurable disease). The immunotherapy 1 (I1) cohort was a phase II, single arm, proof-of-concept substudy evaluating the efficacy of single agent mona. Non-eligible pts for the biomarker-driven cohorts were included in the I1 cohort. Mona was given as an infusion (10 mg/kg) on day 1 of each cycle (14 days). The primary endpoint was objective response rate (RECISTv1.1) during the first 16 weeks. A two-stage Simon design was used (H1 15%, H0 3%, α 8%, power 90%) with planned interruption of accrual if no response was seen after 25 pts. Secondary endpoints included toxicity (CTCAEv4.03), progression-free survival (PFS), response duration and OS. Results 27 RM SCCHN pts were included in the 1st stage (median age: 62 yrs, oral cavity (26%), oropharynx (41%), hypopharynx (26%), larynx (7%)). 16 (59%) were pretreated with anti-PD(-L)1 compounds. No objective response was recorded. Stable disease was observed in 6 pts (22%). Disease progression was recorded in all but one patient and the median PFS was 7.4 wks (95% CI: 6.6-7.9 wks). Based on 16/27 deaths currently recorded, median OS was 27.7 wks (95% CI: 13-53.9 wks). Mona showed a favorable safety profile: 59% pts reported grade  3 adverse events, none of them treatment-related. The final results of these preliminary data will be presented at ESMO. Conclusion The substudy of mona in monotherapy did not meet its primary objective and was closed at interim for futility. Median PFS was 7.4 wks. Mona has a favorable safety profile and is under investigation in combination with durvalumab within the UPSTREAM trial.

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The membrane proximal external region (MPER) of the HIV-1 glycoprotein gp41 is targeted by the broadly neutralizing antibodies 2F5 and 4E10. To date, no immunization regimen in animals or humans has produced HIV-1 neutralizing MPER-specific antibodies. We immunized llamas with gp41-MPER proteoliposomes and selected a MPER-specific single chain antibody (VHH), 2H10, whose epitope overlaps with that of mAb 2F5. Bi-2H10, a bivalent form of 2H10, which displayed an approximately 20-fold increased affinity compared to the monovalent 2H10, neutralized various sensitive and resistant HIV-1 strains, as well as SHIV strains in TZM-bl cells. X-ray and NMR analyses combined with mutagenesis and modeling revealed that 2H10 recognizes its gp41 epitope in a helical conformation. Notably, tryptophan 100 at the tip of the long CDR3 is not required for gp41 interaction but essential for neutralization. Thus bi-2H10 is an anti-MPER antibody generated by immunization that requires hydrophobic CDR3 determinants in addition to epitope recognition for neutralization similar to the mode of neutralization employed by mAbs 2F5 and 4E10.

Autotransporters produced by Gram-negative bacteria consist of an N-terminal signal sequence, a C-terminal translocator domain (TD), and a passenger domain in between. The TD facilitates the secretion of the passenger across the outer membrane. It generally consists of a channel-forming β-barrel that can be plugged by an α-helix that is formed by a polypeptide fragment immediately N-terminal to the barrel domain in the sequence. In this work, we characterized the TD of the hemoglobin protease Hbp of Escherichia coli by comparing its properties with the TDs of NalP of Neisseria meningitidis and IgA protease of Neisseria gonorrhoeae. All TDs were produced in inclusion bodies and folded in vitro. In the case of the TD of Hbp, this procedure resulted in autocatalytic intramolecular processing, which mimicked the in vivo processing. Liposome-swelling assays and planar lipid bilayer experiments revealed that the pore of the Hbp TD was largely obstructed. In contrast, an Hbp TD variant that lacked only one amino-acid residue from the N terminus showed the opening and closing of a channel comparable to what was reported for the TD of NalP. Additionally, the naturally processed helix contributed to the stability of the TD, as shown by chemical denaturation monitored by tryptophan fluorescence. Overall these results show that Hbp is processed by an autocatalytic intramolecular mechanism resulting in the stable docking of the α-helix in the barrel. In addition, we could show that the α-helix contributes to the stability of TDs. © 2011 Informa UK, Ltd.

The lipid A portion of lipopolysaccharide, the major component of the outer leaflet of the outer membrane of Gram-negative bacteria, is toxic to humans. Modification of lipid A by enzymes often reduces its toxicity. The outer-membrane protein LpxR from Salmonella typhimurium is a lipid A-modifying enzyme. It removes the 3′-acyloxyacyl moiety of the lipid A portion of lipopolysaccharide in a Ca2+-dependent manner. Here, we present the crystal structure of S. typhimurium LpxR, crystallized in the presence of zinc ions. The structure, a 12-stranded β-barrel, reveals that the active site is located between the barrel wall and an α-helix formed by an extracellular loop. Based on site-directed mutagenesis and modeling of a substrate on the active site, we propose a catalytic mechanism similar to that of phospholipase A2, in which a Ca2+ forms the oxyanion hole and a histidine activates a water molecule (or a cascade of two water molecules) that subsequently attacks the carbonyl oxygen of the scissile bond.

The first crystal structures of lipases that have been covalently modified through site-selective inhibition by different organometallic phosphonatepincer– metal complexes are described. Two ECE-pincer-type d8-metal complexes, that is, platinum (1) or palladium (2) with phosphonate esters (ECE=[(EtO)-(O=)PACHTUNGTRENUNG(-O-C6H4-ACHTUNGTRENUNG(NO2)- 4)ACHTUNGTRENUNG(-C3H6-4-ACHTUNGTRENUNG(C6H2-ACHTUNGTRENUNG(CH2E)2)] ; E= NMe2 or SMe) were introduced prior to crystallization and have been shown to bind selectively to the Ser120 residue in the active site of the lipase cutinase to give cut-1 (platinum) or cut-2 (palladium) hybrids. For all five presented crystal structures, the ECE-pincer–platplatinum or –palladium head group sticks out of the cutinase molecule and is exposed to the solvent. Depending on the nature of the ECE-pincer–metal head group, the ECE-pincer–platinum and – palladium guests occupy different pockets in the active site of cutinase, with concomitant different stereochemistries on the phosphorous atom for the cut-1 (SP) and cut-2 (RP) structures. When cut-1 was crystallized under halide-poor conditions, a novel metalinduced dimeric structure was formed between two cutinase-bound pincer– platinum head groups, which are interconnected through a single m-Cl bridge. This halide-bridged metal dimer shows that coordination chemistry is possible with protein-modified pincer–metal complexes. Furthermore, we could use NCN-pincer–platinum complex 1 as site-selective tool for the phasing of raw protein diffraction data, which shows the potential use of pincer–platinum complex 1 as a heavy-atom derivative in protein crystallography.