Regulatory perspective on minimal residual disease flow cytometry testing in multiple myeloma

The FDA has co-sponsored three workshops to address minimal residual disease (MRD) detection in acute lymphocytic leukemia (ALL), chronic lymphocytic leukemia (CLL), and acute myeloid leukemia (AML) as well as an FDA-NCI roundtable symposium on MRD detection and its use as a response biomarker in Multiple Myeloma (MM). As clinical outcomes in MM continue to improve with the introduction of new therapeutics, consideration of biomarkers and their development as validated surrogate endpoints that can be used in the place of traditional clinical trial endpoints of progression-free survival (PFS) will be fundamental to expeditious drug development. This article will describe the FDA drug approval process, the regulatory framework through which a biomarker can be used as a surrogate endpoint for drug approval, and how MRD detection in MM fits within this context. In parallel, this article will also describe the FDA current device clearance process with emphasis on the analytical development as it might apply to an in vitro diagnostic assay for the detection of MRD in MM. It is anticipated that this Special Issue may possibly represent how MRD might serve as a drug development tool in hematological malignancies.

Centration of donor trephination in human corneal transplantation

PURPOSE

To develop and evaluate a new method to quantify centration of the trephined donor cornea relative to the limbus.

METHODS

After human donor corneas were trephined for penetrating keratoplasty, the remaining corneoscleral discs were stained and subjected to image analysis. The centration of the excised donor cornea relative to the limbus was calculated by measuring their centroids from the "captured" images.

RESULTS

Fifty-two corneoscleral discs were analyzed. The average deviation from the centre was 0.32 mm (SD, 0.18 mm). Neither surgeon nor the type of trephine significantly influenced the mean centroid deviation.

CONCLUSION

We have developed and evaluated a method to quantify centration of human donor cornea. In a small series, decentration did not correlate significantly with either the surgeon or the trephine.

Socio-biological associations of bacteriuria in pregnancy

The prevalence and socio-biological relations of bacteriuria in Trinidadian pregnant women were investigated. The prevalence of bacteriuria was found to be 16.7% and it was more common in the 30-39 year age group, among parous women, among Negroes, and in patients with a low family income and overcrowded living conditions. Symptoms were present in 19% of bacteriuric patients and almost one-third gave a past history of urinary tract infection. Only 10% had been previously exposed to sexually transmitted diseases such as syphilis, gonorrhea and herpetic genital infections. Because of the serious consequences to mother and foetus, we advocate quantitative urine cultures for all antenatal patients, especially those coming from disadvantaged socio-economic conditions.

Cell attachment to, and contraction of, the retina in vitro

PURPOSE

To examine the behavior of fibroblasts and retinal pigment epithelial cells after attachment to the retinal surface in vitro to elucidate the pathobiology of the early stages of epiretinal membrane formation.

METHODS

Human retinal pigment epithelial (HRPE) cells and bovine Tenon's capsule fibroblasts (BTFs) were seeded onto the surface of bovine retinal explants maintained in organ culture. The changes induced in the underlying retina, including contraction, were assessed during a period of up to 10 days. Immunohistochemistry was used to assess proliferation of the seeded cells and to determine deposition of extracellular matrix.

RESULTS

Explants of bovine neuroretina were maintained in organ culture, with good morphologic preservation of the inner limiting lamina and inner retinal layers, for 7 to 10 days. The HRPE cells and the BTFs attached to the retinal surface and exerted tractional forces, producing partial- and full-thickness retinal folding. Contraction commenced within 24 hours of attachment of the cells and continued for several days, with most of the contraction occurring within the next 48 to 72 hours. The HRPE cells and BTFs were found to be equally contractile. Deposition of cellular fibronectin (but not collagen type I) was demonstrated.

CONCLUSIONS

The contractile cellular membranes generated in this organ culture system exhibit many of the morphologic and functional features of epiretinal membranes found in the early stages of proliferative vitreoretinopathy.

IL-10 and antibodies to TGF-beta2 and PDGF inhibit RPE-mediated retinal contraction

PURPOSE

Retinal pigment epithelial (RPE) cells are believed to play a pivotal role in the formation and contraction of epiretinal membranes in proliferative vitreoretinopathy (PVR). In the present study, an organ culture method was used that mimics the contractile stage of PVR, to investigate the contribution of a variety of growth factors in human RPE cell-mediated contraction of the retina.

METHODS

Cultured human RPE cells were seeded onto bovine retinal explants. After attachment, cultures received one of the following exogenous growth factors: platelet-derived growth factor (PDGF)-AB, PDGF-BB, basic fibroblast growth factor (bFGF), transforming growth factor (TGF)-beta1, TGF-beta2, or interleukin (IL)-10; or a neutralizing antibody to PDGF and/or TGF-beta2. Control explants were either untreated or received a null antibody. Contraction was assessed by image analysis and expressed as percentage reduction in retinal area.

RESULTS

RPE cells produced a more than 50% contraction of the retina after 7 days in untreated samples. PDGF and TGF-beta2 stimulated RPE-mediated contraction by a further 20% at 100 ng/ml. IL-10 decreased contraction by 63%, whereas the other growth factors gave rise to similar contraction to untreated controls. Neutralizing antibodies against PDGF and TGF-beta2 reduced RPE-mediated contraction by up to 70% in comparison with untreated controls. The neutralizing antibodies also inhibited the effects of exogenous PDGF and TGF-beta2 on RPE-mediated contraction of the retina (P < 0.01).

CONCLUSIONS

These findings confirm a role for both PDGF and TGF-beta2 in RPE cell-mediated contraction of the retina. Such contraction can be inhibited by neutralizing antibodies against PDGF and TGF-beta2, which, together with IL-10, are putative candidates for therapeutic intervention in PVR.