AT-101, a small molecule Bcl-2 antagonist, in treatment naïve CLL patients (pts) with high risk features; Preliminary results from an ongoing phase I trial

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Background: CLL pts with early stage disease are often observed under a “watch and wait” approach. Unmutated immunoglobulin variable-region gene (IgVH); expression of zeta chain associated kinase (ZAP-70); CD38 expression; and cytogenetics abnormalities identify pts with a tendency for early disease progression. Whether pts with these high-risk features may benefit from early intervention warrants investigation in clinical trials. Gossypol, a naturally occurring compound in cotton seeds has been extensively studied in clinical trials and is well tolerated with a favorable safety profile. AT-101, a derivative of R-(-)-gossypol binds to Bcl-2 family proteins and induces apoptosis of CLL cells in vitro. Dysregulated expression of Bcl-2 proteins is critical for CLL leukemogenesis and is an attractive therapeutic target. Methods: We conducted a phase I study to evaluate the safety and tolerability of single agent AT-101 in treatment naïve CLL pts with high-risk features. Clinical activity, pharmacokinetics, and pharmacodynamics were assessed. Results: 7 pts were treated with AT-101 at doses of 20–40mg daily. Pt characteristics: median age 55, median Rai stage II, elevated ZAP-70 (57%), high CD38 (71%), unmutated IgVH (57%), trisomy 12 (43%), and loss of 17p (43%). AT-101 was well tolerated with no grade 4 toxicities, hospitalizations, deaths. Maximum toxicity in 6 evaluable pts was grade III transaminase elevation at week 7, with complete resolution following discontinuation of AT-101. Other most common adverse events, all Grade 1–2 include: elevated transaminases; nausea; fatigue; diarrhea; and hypokalemia. No hematologic toxicity was observed. 5/6 pts had decrease in lymphocyte count, 6/6 had reduction in lymphadenopathy, and 5/5 with palpable spleens had reduction in spleen size. Cmax for 30mg (n=3) and 40mg (n=2) dose of AT-101 was 570ng/ml and 660ng/ml at a Tmax of 4.3 and 4.4 hrs. Tmax correlated with in vivo apoptosis studies revealing maximum leukemic cell apoptosis occurring at 4hrs and poly(ADP-ribose) polymerase cleavage. Conclusions: AT-101 is safe and well tolerated, induces in vivo leukemia cell apoptosis, and may have clinical activity in previously untreated pts with CLL and high risk features.

No significant financial relationships to disclose.

Measurement of thermal conductivity of bovine cortical bone

The thermal conductivity of cortical bone was characterized experimentally. Specimens were taken from the mid-diaphysis of bovine femora, and the rate of heat transfer was measured in three orthogonal directions. The conductivity was found to be 0.58+/-0.018 W/mK in the longitudinal direction, 0.53+/-0.030 W/mK in the circumferential direction, and 0.54+/-0.020 W/mK in the radial direction. Because the directional differences are small, it is concluded that bovine cortical bone can be treated as thermally isotropic.

Observation of power-Law scaling for phase transitions in linear trapped ion crystals

We report an experimental confirmation of the power-law relationship between the critical anisotropy parameter and ion number for the linear-to-zigzag phase transition in an ionic crystal. Our experiment uses laser cooled calcium ions confined in a linear radio-frequency trap. Measurements for up to ten ions are in good agreement with theoretical and numeric predictions. Implications on an upper limit to the size of data registers in ion trap quantum computers are discussed.

Temperature rise during drilling through bone

Temperature was measured during drilling in bovine cortical bone specimens. A surgical drill fitted with a custom-designed speedometer and mounted on a drill press was used to drill holes at one speed, 49,000 rpm, and at forces in the range of 1.5 to 9.0 N. The resulting temperatures were recorded by thermocouples placed at various locations. The distribution of maximum local temperature rise (delta T) was best fitted by the function delta T = aR-b, where R is the distance from the center of the drilled hole and a and b are constants that were found by regression analysis. It was also found that the temperature increased with force, up to about 4.0 N, and then decreased at forces greater than that because of decreased drilling time. A separate series of tests revealed that temperatures were higher in the longitudinal direction than in the circumferential direction; this difference was attributed to the anisotropic thermal properties of bone.

Measurements of shaft speed while drilling through bone

PURPOSE

This study investigated the effect of force on drill speed and measured the energy consumed during the drilling process.

MATERIAL AND METHODS

Applied force, drill speed, and energy consumed were measured during drilling in bovine cortical bone specimens. A commercial surgical drill was fitted with a custom-designed speedometer for measuring the rotational speed. The handpiece was attached to a laboratory drill press and positioned above a bone specimen mounted on a load cell. To apply steady loads, weights were placed on the drill platform, and tests were conducted for forces between 1.5 and 9.0 N and for free-running speeds from 20,000 to 100,000 rpm.

RESULTS

The simultaneous measurements of speed and load for the electrically powered instrument showed that the average operating speed changed with the force applied: at low starting speeds, the speed increased slightly with force; at high starting speeds, the speed decreased with force by as much as 50%. The measurements of electric power showed that the total energy consumed generally decreased with speed and force, primarily because of decreased drilling time.

CONCLUSION

The decrease in energy suggests that drilling at high speed and with a large force may be desirable because bone temperature is reduced.

Force and moment distributions among osseointegrated dental implants

Distributions of force, bending moment and torque are determined by structural analysis for an osseointegrated dental implant system. The system is a dental prosthesis rigidly connected to bone by implants. Since the implants have the lowest flexural rigidity of the structural components, they are considered to be the only elastic components of the system. In the analysis, the number and position of the implants are variable and the magnitude, direction and location of the applied load are arbitrary. The distributions found by force and moment balances are in the form of simple algebraic equations, a form which is useful for clinicians in determining the number and location of implants so that forces and moments are shared equitably. One immediate result of the structural analysis is that the bending moment due to the vertical component of the applied load--a moment which has previously been neglected--can produce stresses in the implant which are an order of magnitude larger than the direct axial stresses.

Load transfer to abutment teeth by two non-metal adhesive bridges

Recently, two alternatives to the etched metal, Maryland-type bridge have been proposed for anterior applications. These are the all-ceramic bridge and the composite resin framework, ceramic veneered pontic bridge. Both designs use acid-etched winged retainers for adhesion. The purpose of this study was to evaluate the load transfer to abutment teeth by these two designs using photoelastic modeling.

An experimental evaluation of spinal flexibility with respect to scoliosis surgery

Lateral flexibility of the spinal column was investigated by mechanical analysis and by experiments on fresh cadavers. The work was undertaken with the aim of improving the surgical treatment of scoliosis by quantifying the effects of ribs and transverse processes on lateral spinal flexibility. To this end, flexibilities before and after removal of the bony elements in cadavers' spines were compared. A portable instrument was built to apply loads to the spines. Generally, the spines were tested in the following sequence of conditions: intact, resected ribs on one side, resected ribs and transverse processes on the same side. The results from nine cadavers indicate that only rib resection on the tension side of the induced curve (scoliotic concavity) significantly increased spinal flexibility. It is concluded that the surgical correction of scoliotic curves with instrumentation and fusion is maximized with rib osteotomy or resection.

The hydrodynamic resistance of hyaluronic acid and its contribution to tissue permeability

An experimental system was developed to measure flow rates and pressure drops across hyaluronic acid solutions. The solutions were contained by membranes in a test cell, and solvent was perfused through the cell at flow rates comparable to physiological conditions. The pressure drop was found to be proportional to a steady flow rate for concentrations up to 1.5%, confirming that Darcy's Law for porous media is valid for hyaluronic acid solutions (and indicating that the polymer chains did not pile up at one end of the test cell). From the flow data, the hydrodynamic permeability of each solution was calculated and found to be 50 times higher that whole tissue having the same hyaluronic acid concentration; hyaluronic acid on its own, therefore, is not the source of resistance to flow in tissue. The results for hyaluronic acid were then used to show that all the glycosaminoglycans together cannot cause the high resistance of ground substance in tissue, and it is argued that mucoproteins are the most likely source. A hydrodynamic model of the polymer chains was developed to predict solution permeability; the theoretical values agree closely with the experimental data.

Forces in the metacarpophalangeal joint due to elevated fluid pressure--analysis, measurements and relevance to ulnar drift

The mechanics of the metacarpophalangeal joint are analyzed, with a view to understanding why the finger moves in the direction of ulnar drift when the intra-articular pressure in the joint is increased. The first step is the in situ measurement of stiffness of the various tissues surrounding the joint, and the data show that (a) the two collateral ligaments are the major component and (b) the ulnar ligament is the stiffer. This latter result, combined with finding the centre of pressure at the base of the phalanx, reveals how increased intra-articular pressure produces ulnar deviation. Flexion, the other component of ulnar drift, is produced because of the volar side attachment of the ligaments. The mechanics are evaluated quantitatively by the measurement of forces at the finger tip for various pressures; the data agree reasonably well with predictions using the measured joint properties in a simplified mechanical model of the joint.

Analysis of the urethral pressure profile using a mechanical model

Using a model of the urethra designed to ensure a predictable pressure profile along its length, we investigated optimal parameters for gas and water profilometry. In gas profilometry, the response characteristics of the machine, attributable to the highly compressible nature of gas, were shown to be the most important determinants of accuracy. Gas and water profilometry have drawbacks that make clinical results inaccurate. However, if all measuring parameters are carefully recorded and considered when a pressure profile is analyzed, system error can be decreased from 62 to 5% by using the optimal pull and flow rates determined by this study.

Intra-articular pressure as a factor in initiating ulnar drift

To determine the possible relevance of intra-articular pressure in the production of ulnar drift, metacarpophalangeal joints of fresh cadaver specimens were injected with water to increase the intra-articular pressure. Of the thirty-two joints tested, ulnar deviation was produced in twenty-three, flexion in twenty-four, and simultaneous ulnar deviation and flexion (ulnar drift) in nineteen. In two or three instances, the displacement was in extension or radial deviation. These results suggest that elevated intra-articular pressure may be a factor in the initiation of ulnar drift in patients with rheumatoid arthritis.