Kinetics and Characterization of Non-enzymatic Fragmentation of Monoclonal Antibody Therapeutics

Purpose

To understand non-enzymatic hydrolytic fragmentation of a monoclonal antibody therapeutic under temperature stressed conditions and investigating possible mechanism for the same.

Methods

The mAb therapeutic was incubated at 50°C in phosphate buffer at pH 6.5 and fragmentation was monitored at different ionic strengths under stressed conditions. The incubated mAb was sampled at regular time intervals by analytical Size Exclusion Chromatography (SEC).

Results

It was observed that 57% of the mAb product fragmented over 4 days into two fragment species – Fc-Fab and Fab with molecular weights of 97 KDa and 47 KDa, respectively, as measured by mass spectrometry (MS) and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The fragmentation rate was slow initially and then accelerated with time. No change in % aggregate level was observed in this duration, implying that degradation was primarily via fragmentation at high temperature. Kinetics of hydrolytic fragmentation was hypothesized and SEC data was fitted to estimate the kinetic rate constants. While degradation of the monomer into fragment species was non-Arrhenius with a negative activation energy, further degradation of Fab-Fc fragments into Fab or Fc fragments followed Arrhenius Law with an activation energy of 2.1 and 15.38 kcal/mol, respectively.

Conclusion

High temperature (50°C) causes mAb to cleave at the hinge region to form Fab-Fc and Fab/Fc, as confirmed by dynamic light scattering, SDS-PAGE, SEC, and MS. A kinetic model for hydrolytic fragmentation has been proposed. The results are expected to assist end users in formulation development as well as in monitoring stability of biotherapeutic products.

     

N-nitrosodimethylamine-derived O6-methylguanine in DNA of monkey gastrointestinal and urogenital organs and enhancement by ethanol

N-nitrosodimethylamine (NDMA) is a human cancer initiator suspect. Ethanol, a cancer risk factor, may synergize with nitrosamines by suppressing hepatic clearance, to increase internal exposure. A limitation to these hypotheses is lack of activation of NDMA by many rodent tissues. However, systematic primate studies are lacking. Patas monkeys were utilized to investigate NDMA activation by primate tissues in vivo, generating the promutagenic DNA lesion O⁶-methylguanine (O⁶-meG). Adult monkeys received 0.1 mg/kg NDMA by gavage, in some cases preceded by ethanol. Four hours after NDMA only, O⁶-meG was detected in DNA from all tissues. Levels were highest in gastric mucosa and liver and were only about 50% lower in DNA from white blood cells, esophagus, ovary, pancreas, urinary bladder and uterus. With ethanol co-exposure, amounts of O⁶-meG increased at least 2-fold in all tissues except liver. The largest effect was in esophagus (17-fold increase), followed by ovary, large intestine, urinary bladder, spleen and cerebellum (9- to 13-fold increases), and uterus, cerebrum and brain stem (7- to 8-fold increases). Alkylguanine alkyltransferase activities varied over a 30-fold range and were highest in liver and stomach. Thus primate tissues, especially those of the gastrointestinal and urogenital organs, are sensitive targets for DNA adduct damage due to NDMA, and ethanol co-exposure leads to striking increases in adducts. Our data support epidemiology implicating nitrosamines in causation of cancers of stomach and other organs, and alcohol as enhancing internal exposure to nitrosamines. © 1996 Wiley-Liss, Inc.     

Mechanical breakdown and thrombolysis in subacute massive pulmonary embolism: A prospective trial

AIM: To assess role of combined modality of mechanical fragmentation and intralesional thrombolysis in patients with massive pulmonary embolism presenting subacutely. METHODS: Eight of 70 patients presenting in tertiary care centre of North India with massive pulmonary embolism within 4 years had subacute presentation (symptom onset more than 2 wk). These patients were subjected to pulmonary angiography with intention to treat basis via mechanical breakdown and intra lesional thrombolysis. Mechanical breakdown of embolus was accomplished with 5-F multipurpose catheter to reestablish flow, followed by intralesional infusion of urokinase (4400 IU/kg over 10 min followed by 4400 IU/kg per hour over 24 h). RESULTS: Eight patients, mean age 47.77±12.20 years presented with subacute pulmonary embolism (mean duration of symptoms 2.4 wk). At presentation, mean heart rate, shock index, miller score and mean pulmonary pressures were 101.5±15.2/min, 0.995±0.156, 23.87±3.76 and 37.62±6.67 mmHg which reduced to 91.5±12.2/min (P=0.0325), 0.789±0.139 (P=0.0019), 5.87±1.73 (P=0.0000004) and 27.75±8.66 mmHg (P=0.0003) post procedurally. Mean BP improved from 80.00±3.09 mmHg to 90.58±9.13 mmHg (P=0.0100) post procedurally. Minor complications in the form of local hematoma-minor hematoma in 1 (12.5%), and pseudoaneurysm (due to femoral artery puncture) in 1 (12.5 %) patient were seen. At 30 d and 6 mo follow up survival rate was 100% and all the patients were asymptomatic and in New York Heart Association class 1. CONCLUSION: Combined modality of mechanical fragmentation and intralesional thrombolysis appears to be a promising alternative to high risk surgical procedures in patients with subacute massive pulmonary embolism.     

A cost effective endovascular approach for management of post-catheterization profunda femoris artery pseudoaneurysm using thrombin

Post-catheterization PSA is one of the most commonly encountered vascular complications of cardiac and peripheral angiographic procedures. We report the case of patient who developed deep-seated profunda femoris artery pseudoaneurysm (PSA) following cardiac catheterization. Despite, repeated ultrasound guided compressions the PSA failed to close and instead produced local site pressure ulcers. The secondary infection followed which precluded use of percutaneous thrombin injection. The PSA was finally closed via a total endovascular technique combining intravascular thrombin injection and coil embolization, thus obviating the need for expensive measures like cover stents or invasive surgical repairs.     

Multiple subpial lipomas with dumb-bell extradural extension through the intervertebral foramen without spinal dysraphism

BACKGROUND: Intradural subpial lipomas not associated with spinal dysraphism, account for less than 1% of spinal cord tumors. The simultaneous existence of multiple intradural subpial lipomas with dumb-bell extradural extension through the intervertebral foramen in the same patient without any evidence of spinal dysraphism has not been previously reported. CASE DESCRIPTION: A 38-year-old man presented with progressive spastic paraparesis, and weakness of right elbow extension and opposition of the medial three fingers. He also had ascending paraesthesia from the C6 dermatome to the saddle region and loss of joint and position sense of both lower limbs with hesitancy and precipitancy of micturition. There was no spinal tenderness, deformity, neurocutaneous markers, or spinal dysraphism. The total duration of illness was 11 years.The oblique views of the plain radiographs of the cervical spine revealed an enlarged right C7-D1 intervertebral foramen. The T1- and T2-weighted magnetic resonance (MR) images showed two intradural, hyperintense lesions (with extensive loss of signal on fat suppression sequences), one extending from C5 to D2 and the other opposite the C3-4 disc space. The parasagittal and axial images showed the extradural component of the lesion emerging from the right C7-D1 intervertebral foramen.At surgery, a C2 to D2 laminectomy was performed. The lipoma, enclosed in a fine pial membrane, was situated on the right posterolateral aspect of the cord. The right-sided nerve roots from the C6 to D1 levels were completely enmeshed by the lipoma. There was a separate superficial subpial lipoma adherent to the posterior aspect of the cord at the C3-4 level. A distinct area of normal cord was present between the two lesions. A subtotal decompression of the lesions including the component emerging through the right C7-D1 intervertebral foramen and a duraplasty were performed.At follow-up after 18 months, the posterior column impairment, lower limb hypoaesthesia, and right upper limb paraesthesia had improved. However, residual elbow extension and lower limb weakness, mild lower limb spasticity and sphincteric dysfunction persisted. CONCLUSIONS: The multiplicity of intradural subpial lipomas without spinal dysraphism points to a dysembryogenetic basis similar to that seen in patients with spinal dysraphism that results in lipomas, but in which the defect is not severe enough to give rise to coexisting vertebral and soft tissue anomalies. The dumb-bell extradural extension through the intervertebral foramen is extremely rare. The magnetic resonance imaging and surgical principles are discussed.     

Recurrent intramedullary cervical ependymal cyst

We report a rare case of high cervical intramedullary ependymal cyst in a young boy. This was associated with atlantoaxial dislocation. After partial removal and marsupialization, the cyst recurred and needed radical total resection.