A comparison of the activity, lysosomal stability, and efficacy of legumain-cleavable and cathepsin cleavable ADC linkers.

1. Over the past two decades antibody-drug conjugates (ADCs) have emerged as a highly effective drug delivery technology. ADCs utilize a monoclonal antibody, a chemical linker, and a therapeutic payload to selectively deliver highly potent pharmaceutical agents to specific cell types.2. Challenges such as premature linker cleavage and clearance due to linker hydrophobicity have adversely impacted the stability and safety of ADCs. While there are various solutions to these challenges, our team has focused on replacement of hydrophobic ValCit linkers (cleaved by CatB) with Asn-containing linkers that are cleaved by lysosomal legumain.3. Legumain is abundantly present in lysosomes and is known to play a role in tumor microenvironment dynamics. Herein, we directly compare the lysosomal cleavage, cytotoxicity, plasma stability, and efficacy of a traditional cathepsin cleavable ADC to a matched Asn-containing legumain-cleavable ADC.4. We demonstrate that Asn-containing linker sequences are specifically cleaved by lysosomal legumain and that Asn-linked MMAE ADCs are broadly active against a variety of tumors, even those with low legumain expression. Finally, we show that AsnAsn-linked ADCs exhibit comparable or improved efficacy to traditional ValCit-linked ADCs. Our study paves the way for replacement of the traditional ValCit linker technology with more hydrophilic Asn-containing peptide linker sequences.

ValCitGlyPro-dexamethasone antibody conjugates selectively suppress the activation of human monocytes.

Glucocorticoids (GCs) are effective in treating autoimmune and inflammatory disorders but come with significant side effects, many of which are mediated by non-immunological cells. Therefore, there is rapidly growing interest in using antibody drug conjugate (ADC) technology to deliver GCs specifically to immune cells, thereby minimizing off-target side effects. Herein, we report the study of anti-CD11a, anti-CD38, and anti-TNFα ADCs to deliver dexamethasone to monocytes. We found that anti-CD11a and anti-CD38 were rapidly internalized by monocytes, while uptake of anti-TNFα depended on pre-activation with LPS. Using these antibodies were attached to a novel linker system, ValCitGlyPro-Dex (VCGP-Dex), that efficiently released dexamethasone upon lysosomal catabolism. This linker relies on lysosomal cathepsins to cleave after the ValCit sequence, thereby releasing a GlyPro-Dex species that undergoes rapid self-immolation to form dexamethasone. The resulting monocyte-targeting ADCs bearing this linker payload effectively suppressed LPS-induced NFκB activation and cytokine release in both a monocytic cell line (THP1) and in human PBMCs. Anti-TNFα_VCGP-Dex and anti-CD38_VCGP-Dex were particularly effective, suppressing ∼60-80% of LPS-induced IL-6 release from PBMCs at 3-10 µg mL-1 concentrations. In contrast, the corresponding isotype control ADC (anti-RSV) and the corresponding naked antibodies (anti-CD38 and anti-TNFα) resulted in only modest suppression (0-30%) of LPS-induced IL-6. Taken together, these results provide further evidence of the ability of glucocorticoid-ADCs to selectively suppress immune responses, and highlight the potential of two targets (CD38 and TNFα) for the development of novel immune-suppressing ADCs.

Experiences of an outpatient infusion center with intravenous magnesium therapy for status migrainosus.

OBJECTIVES: Exploratory study to investigate the effectiveness of intravenous magnesium as an abortive for status migrainosus in an outpatient infusion center, and characterize the patients who benefit from the therapy. PATIENTS & METHODS: Retrospective analysis of 234 migraine patients who received IV magnesium as a headache abortive, at the headache clinic of University of Southern California. Additional intramuscular (IM) injections for nausea (prochlorperazine, odansetron, metoclopramide) or for refractory pain (ketorolac, dexamethasone, sumatriptan, dihydroergotamine), were administered as necessary. Immediately before and after treatment, self-reported pain levels were recorded using an 11-point numeric pain rating scale (0-10). RESULTS: Our patient sample has a mean age of 44 years and was predominantly female (79%). 36 (19%) had migraine with aura. Overall, pain score decreased from 5.46±2.39 to 3.56 ± 2.75 (P < 0.001) after magnesium infusion. One hundred twenty-seven (54%) patients had clinically significant pain reduction, as defined by pain decrease ≥ 30%. One hundred and four patients (44%) received IV magnesium and did not require additional intramuscular (IM) medications for pain. In patients who did not receive additional IM medications for pain, pain score decreased from 4.76 ± 2.41 to 2.95 ± 2.70 (p < 0.001), and 61 out of 104 (59%) experienced ≥ 30% pain reduction. Patients with less severe pain tended to have a better response than patients with more severe pain, as patients with ≥30% pain reduction had a significantly lower pre-treatment pain score (p = 0.018). CONCLUSION: For a subset of patients with status migrainosus, IV magnesium therapy results in clinically significant pain relief without the need for intramuscular pain medications. Therefore, IV magnesium may be useful as a cost-effective first-line parental therapy for status migrainosus, especially for patients who initially present with lower pain intensity.