Aspire Capital is a growth equity firm focused on making direct investments into public companies across various industries. This time around, the firm picked a player in the fast-developing--and already packed--realm of liquid biopsy for cancer diagnostics and monitoring. It's made a $15 million stock purchase agreement with molecular diagnostics company Biocept.

The San Diego, CA-based micro-cap is focused on blood-based liquid biopsies to be used to detect, monitor and determine treatment for cancer. Earlier this month, Biocept disclosed a couple of partnership milestones: one to do a proof-of-concept study in collaboration with Rosetta Genomics ($ROSG) to determine the usefulness of microRNA profiling of circulating tumor cells as part of lung cancer diagnostics, and the other with Baylor College of Medicine to develop a liquid biopsy test for mutations in the estrogen receptor gene, which play a role in identifying the roughly one-third of breast cancer patients who may easily become resistant to Tamoxifen and other endocrine therapies.

"Liquid biopsy represents a fundamental shift in how cancer patients can be diagnosed and monitored, which we strongly believe will translate into better treatment decisions and outcomes," said Aspire Capital Managing Member Steven Martin in a statement. "Biocept is uniquely positioned to capitalize on this opportunity through its capability of assaying both circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA)."