Bispecific T-Cell Redirection versus Chimeric Antigen Receptor (CAR)-T Cells as Approaches to Kill Cancer Cells

The concepts for T-cell redirecting bispecific antibodies (TRBAs) and chimeric antigen receptor (CAR)-T cells are both at least 30 years old but both platforms are just now coming into age. Two TRBAs and two CAR-T cell products have been approved by major regulatory agencies within the last ten years for the treatment of hematological cancers and an additional 53 TRBAs and 246 CAR cell constructs are in clinical trials today. Two major groups of TRBAs include small, short-half-life bispecific antibodies that include bispecific T-cell engagers (BiTE®s) which require continuous dosing and larger, mostly IgG-like bispecific antibodies with extended pharmacokinetics that can be dosed infrequently. Most CAR-T cells today are autologous, although significant strides are being made to develop off-the-shelf, allogeneic CAR-based products. CAR-Ts form a cytolytic synapse with target cells that is very different from the classical immune synapse both physically and mechanistically, whereas the TRBA-induced synapse is similar to the classic immune synapse. Both TRBAs and CAR-T cells are highly efficacious in clinical trials but both also present safety concerns, particularly with cytokine release syndrome and neurotoxicity. New formats and dosing paradigms for TRBAs and CAR-T cells are being developed in efforts to maximize efficacy and minimize toxicity, as well as to optimize use with both solid and hematologic tumors, both of which present significant challenges such as target heterogeneity and the immunosuppressive tumor microenvironment

Engineering host cell lines to reduce terminal sialylation of secreted antibodies

Covalently-linked glycans on proteins have many functional roles, some of which are still not completely understood. Antibodies have a very specific glycan modification in the Fc region that is required for mediating immune effector functions. These Fc glycans are typically highly heterogeneous in structure, and this heterogeneity is influenced by many factors, such as type of cellular host and rate of Ab secretion. Glycan heterogeneity can affect the Fc-dependent activities of antibodies. It has been shown recently that increased Fc sialylation can result in decreased binding to immobilized antigens and some Fcγ receptors, as well as decreased antibody-dependent cell-mediated cytotoxicity (ADCC) activity. In contrast, increased Fc sialylation enhances the anti-inflammatory activity of antibodies. To produce antibodies with increased effector functions, we developed host cell lines that would limit the degree of sialylation of recombinantly-expressed antibodies. Towards this end, the catalytic domain of the Arthrobacter ureafaciens sialidase (sialidase A) was engineered for secreted expression in mammalian cell lines. Expression of this sialidase A gene in mammalian cells resulted in secreted expression of soluble enzyme that was capable of removing sialic acid from antibodies secreted into the medium. Purified antibodies secreted from these cells were found to possess very low levels of sialylation compared with the same antibodies purified from unmodified host cells. The low sialylated antibodies exhibited similar binding affinity to soluble antigens, improved ADCC activity, and they possessed pharmacokinetic properties comparable to their more sialylated counterparts. Further, it was observed that the amount of sialidase A expressed was sufficient to thoroughly remove sialic acid from Abs made in high-producing cell lines. Thus, engineering host cells to express sialidase A enzyme can be used to produce recombinant antibodies with very low levels of sialylation

Metamorphosen.

Latin and German on opposite pages.1. Bd. Buch I-VII, erklärt von Moritz Haupt. 10. Aufl. Unveränderte Neuausg. der 9 Aufl. von Rudolf Ehwald, Korrigiert und bibliographisch erg. von Michael von Albrecht.--2. Bd. Buch VIII-XV, im Anschluss an Moritz Haupts Bearbeitung der Bücher 1-7 erklärt von Otto Korn. 5 Aufl. Unveran̈derte Neuausg. der 4. Aufl. von Rudolf Ehwald, korrigiert und bibliographisch erg. von Michael von Albrecht

Osteochondral Allograft Transplant to the Medial Femoral Condyle Using a Medial or Lateral Femoral Condyle Allograft

BackgroundOsteochondral allograft (OCA) transplantation is an effective treatment for defects in the medial femoral condyle (MFC), but the procedure is limited by a shortage of grafts. Lateral femoral condyles (LFCs) differ in geometry from MFCs but may be a suitable graft source. The difference between articular surface locations of the knee can be evaluated with micro-computed tomography imaging and 3-dimensional image analysis.HypothesisLFC OCAs inserted into MFC lesions can provide a cartilage surface match comparable with those provided by MFC allografts.Study designControlled laboratory study.MethodsTwenty MFCs and 10 LFCs were divided into 3 groups: 10 MFC recipients (MFCr), 10 MFC donors (MFCd), and 10 LFC donors (LFCd). A 20-mm defect was created in the weightbearing portion of the MFCr. Two grafts, 1 MFCd and 1 LFCd, were implanted sequentially into each MFCr. Micro-computed tomography (μCT) images of the MFCr were acquired and analyzed to compare the topography of the original recipient site with the MFCd- and LFCd-repaired sites. Three-dimensional transformations were defined to register the defect site in the 3 scans of each MFCr. Vertical deviations from each voxel of the graft cartilage surface, relative to the intact recipient cartilage surface, were calculated and assessed as root mean square deviation and percentage graft area that was proud, sunk, and within the "acceptable" distance (±1.00 mm). The effect of repair (with MFC vs with LFC) on each of the surface match parameters is presented as mean ± SD and was assessed by t test: height deviation over area (root mean square, mm), graft area acceptable (%), area unacceptably proud (%), area unacceptably sunk (%), step-off height over circumference (root mean square, mm), graft circumference acceptable (%), circumference unacceptably proud (%), and circumference unacceptably sunk (%). Percentage data were arcsin transformed before statistical testing. An alpha level of 0.05 was used to conclude if variations were statistically significant.ResultsMFCr defects were filled with both orthotopic MFCd and nonorthotopic LFCd. Registered μCT images of the MFCr illustrate the cartilage surface contour in the sagittal and coronal planes, in the original intact condyle, as well as after OCA repairs. Specimen-specific surface color maps for the MFCr after implant of the MFCd and after implant of LFCd were generally similar, with some deviation near the edges. On average, the MFCr site exhibited a typical contour, and the MFCd and LFCd were slightly elevated. Both types of OCA-MFCd and LFCd-matched well, showing overall height deviations of 0.63 mm for area and 0.47 mm for step-off, with no significant difference between MFCd and LFCd (P = .92 and .57, respectively) and acceptable deviation based on area (87.6% overall) and step-off (96.7% overall), with no significant difference between MFCd and LFCd (P = .87 and .22, respectively). A small portion of the implant was proud (12.1% of area and 2.6% of circumference step-off height), with no significant difference between MFCd and LFCd (P = .26 and .27, respectively). A very small portion of the implant area and edge was sunk (0.3% of area and 0.6% of circumference), with no significant difference between MFCd and LFCd (P = .29 and .86, respectively).Conclusion/clinical relevanceThe achievement of excellent OCA surface match with an MFCd or LFCd graft into the common MFCr site suggests that nonorthotopic LFC OCAs are acceptable graft options for MFC defects