CytomX Therapeutics (NASDAQ: CTMX) drew attention a few days ago after its six-year-old, up-to-$1.68 billion cancer collaboration with Astellas Pharma (Tokyo: 4503) was terminated by the Japanese pharma giant, but the setback hardly registered with investors of the South San Francisco, CA, biotech. Instead, what drew investors to CytomX stock on March 16 was its announcement of positive dose expansion data from a Phase I trial (NCT06265688) assessing varsetatug masetecan (varseta-M) in metastatic colorectal cancer (mCRC). Varseta-M achieved an overall response rate (ORR) of 32% and a median progression-free survival (mPFS) of 7.1 months at the high dose of 10 mg/kg. “We continue to be highly encouraged by what we’re seeing, and we aim to develop varseta-M aggressively for the benefit of patients with CRC and over time, many other cancers,” Sean A. McCarthy, D.Phil., CytomX’s CEO and chairman, told analysts on the company’s quarterly earnings call on March 16. CytomX basked in the glow of that news as its shares rocketed 75%, soaring from $4.68 to $8.20 early in trading before settling for a 44% gain and a closing price that day of $6.75. But the stock went downhill the following two days, as CytomX shares tumbled 19% to $5.45 Tuesday, then skidded another 19% Wednesday to $4.40. The 35% nosedive was reversed on Thursday when CytomX shares rebounded 9% to $4.78. But the company gave up most of that gain Friday, through a 7% drop that sent the stock finishing the week at $4.45—down 5% from a week…
