Pliant Therapeutics, Inc. (NASDAQ:PLRX) released on Monday data from the first three of five potential cohorts of its ongoing Phase 1 dose escalation trial of PLN-101095, in combination with Merck & Co Inc.’s (NYSE:MRK) Keytruda (pembrolizumab), in patients with immune checkpoint inhibitor (ICI)-refractory advanced or metastatic solid tumors.

Interim results demonstrated PLN-101095 antitumor activity in combination with pembrolizumab, with three partial responses observed in cohort three at the 1000 mg administered orally twice daily (BID) dose, representing a 50% objective response rate (ORR) at the highest dose tested to date.

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PLN-101095 was generally well tolerated across all doses tested.

Nine patients with six different tumor types were enrolled in cohorts one through three of the trial.

Patients were treated for 14 days with PLN-101095 at doses of 250 mg, 500 mg or 1000 mg administered orally BID, followed by treatment with a combination of PLN-101095 and pembrolizumab at 200 mg administered intravenously every three weeks (Q3W): 

• Across all doses tested, PLN-101095 was generally well tolerated.
• Of the six patients treated at the 1000 mg BID dose of PLN-101095, three (50%) confirmed partial responses were observed. All three patients remain on treatment.
  • Non-Small Cell Lung Cancer (NSCLC): Confirmed partial response with a 74% reduction in tumor size at Week 18; initial partial response was observed at Week 10.
  • Cholangiocarcinoma: Confirmed partial response with a 48% reduction in tumor size at Week 42; initial partial response was observed at Week 34.
  • Melanoma: Confirmed partial response with a 42% reduction in tumor size at Week 27; initial partial response was observed at Week 18.

The Phase 1 trial of PLN-101095 is currently enrolling the fourth of five potential cohorts. The fourth cohort is evaluating PLN-101095 at 1000 mg, three times daily (TID).

PLRX Price Action: Pliant Therapeutics stock is up 12.99% at $1.74 at publication Monday.

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