Rationale: CALAA-01 is a targeted therapeutic designed to inhibit tumor growth and/or reduce tumor size. The active ingredient in CALAA-01 is a small interfering RNA (siRNA). This siRNA inhibits tumor growth via RNA interference to reduce expression of the M2 subunit of ribonucleotide reductase (R2). The CALAA-01 siRNA is protected from nuclease degradation within a stabilized nanoparticle targeted to tumor cells.