Rubius Therapeutics (RUBY) Reports Initial Clinical Data from Ongoing Phase 1/2 Trial of RTX-240 in Patients with Advanced Solid Tumors, Demonstrating Single-Agent Activity

March 15, 2021 7:39 AM EDT
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Rubius Therapeutics, Inc. (Nasdaq: RUBY), a clinical-stage biopharmaceutical company that is genetically engineering red blood cells to create an entirely new class of cellular medicines called Red Cell Therapeutics™, today announced initial clinical, pharmacodynamic and tumor trafficking data from its ongoing Phase 1/2 clinical trial of RTX-240 in patients with advanced solid tumors. The Company also shared tumor trafficking data from one patient with relapsed/refractory acute myeloid leukemia (AML) in the second Phase 1 arm of the study. The Company believes these data provide initial proof-of-concept of the RED PLATFORM® by providing evidence that red blood cells can be engineered to mimic the human immune system and stimulate adaptive and innate immunity to generate clinical responses in cancer patients with refractory disease.

“These initial data are incredibly exciting and demonstrate that RTX-240 has the potential to generate single-agent activity in patients with solid tumors, including a cold tumor such as metastatic uveal melanoma, where other treatments have failed to induce responses in patients,” said Christina Coughlin, M.D., Ph.D., chief medical officer at Rubius Therapeutics. “The encouraging safety results, including a single event of Grade 1 liver toxicity, and preliminary efficacy data for RTX-240 to date give us the potential to realize the power of immune agonists for the treatment of cancer.”

Initial Efficacy Data

Five (5) dose cohorts were completed in the solid tumor trial at the time of the data cutoff on February 28, 2021 (n=16), with 16 patients evaluable for safety (primary outcome measure) and 15 patients evaluable for efficacy (secondary outcome measure) based on RECIST v1.1.

The study is continuing to enroll patients and despite the fact that dose optimization is still ongoing, RTX-240 generated:

  • A confirmed partial response (PR) with a 54% reduction in the target lesions at the 1e8 dose administered every 4 weeks in a patient with metastatic anal cancer whose disease had progressed on anti-PD-L1 therapy. Treatment of this patient was ongoing 8 months following the first dose at data cutoff;
  • An unconfirmed PR with complete resolution of the target hepatic lesion and resolution of 14/15 hepatic lesions at the 1e10 dose administered every 4 weeks in a patient with metastatic uveal melanoma whose disease had progressed on anti-PD-1 therapy. Treatment of this patient was ongoing 4 months following the first dose at data cutoff; and
  • Stable disease (SD) was observed in 6 patients, including 4 individual patients with stable disease for at least 12 weeks:
    • Non-small cell lung cancer (disease stabilization for 12 weeks with treatment ongoing as of the data cutoff);
    • Soft tissue sarcoma (disease stabilization for 4 months);
    • Pancreatic cancer (disease stabilization for 3 months); and
    • Prostate cancer (disease stabilization for 4 months).

“We believe these data provide clinical validation of our RED PLATFORM® and de-risk our oncology pipeline of Red Cell Therapeutics,” said Pablo J. Cagnoni, M.D., president and chief executive officer. “Given the encouraging initial safety and preliminary efficacy data for RTX-240, we plan to initiate a Phase 2 expansion cohort in the first quarter of 2022, and a new Phase 1 arm of the ongoing RTX-240 clinical trial to evaluate RTX-240 in combination with anti-PD-1 therapy in patients with advanced solid tumors during the second half of 2021.”

Initial Safety Data

The most common treatment-related Grade 1/2 adverse events were fatigue (n=4), chills, nausea, decreased appetite and arthralgias all reported in 3 patients each. There were no treatment-related Grade 3/4 adverse events, no dose-limiting toxicities and a single Grade 1 event of liver toxicity.

Ten (10) immune-related adverse events (irAE) were observed among 5 patients with no reported treatment-related Grade 3/4 irAEs. Grade 2 treatment-related irAEs included pneumonitis (n=1), adrenal insufficiency (n=1) and hypothyroidism (n=1).

Pharmacodynamic Data

In addition to evaluating safety and preliminary efficacy data, the trial is evaluating the pharmacodynamic effects of RTX-240:

  • RTX-240 stimulated innate and adaptive immunity as demonstrated by the activation and/or expansion of NK or memory CD8+ T cells in all patients, with 9/16 patients showing activation and expansion in both cell types. There was an overall trend towards a dose response in absolute NK cell numbers (expansion);
  • Detailed NK cell analysis showed an increased percentage of CD16+CD56dim (mature NK cells) and CD56bright (immature NK cells) across dose levels
    • These cell subtypes are associated with cytotoxicity and cytokine production respectively; and
  • RTX-240 induced expression of key NK cell activation receptors, including NKp30 and the ratio of cells expressing the activation receptor NKG2D versus the inhibitory receptor NKG2A
    • This specific signature of NK cell receptor expression may allow selection of specific tumor types with predicted sensitivity to RTX-240.

Tumor Infiltration Data

Immune cell trafficking into the tumor microenvironment (TME) was assessed by tumor biopsies from participating patients with solid tumors (optional; n=4) and AML (standard of care; n=1).

  • Trafficking of T and NK cells into the TME was observed in 3/5 patients (1.6 to 10-fold increases), including one patient each with metastatic mesothelioma, metastatic soft tissue sarcoma and refractory AML. Tumor infiltration was not observed in patients with ovarian cancer (n=1) and heavily pretreated melanoma (n=1);
  • There was increased expression of PD-L1 observed in 3/4 patients with solid tumors, suggesting an improved immune-permissive TME; and
  • In one patient with AML, trafficking of T and NK cells into the bone marrow was associated with increases in the cellularity of the marrow.

Upcoming Anticipated Milestones

In order to realize the full potential of RTX-240, the Company’s other oncology programs and the RED PLATFORM, in the next 12 months, Rubius plans to execute several critical milestones:

  • Present additional clinical results from the RTX-240 solid tumor Phase 1 clinical trial;
  • Select the recommended RTX-240 Phase 2 dose, schedule and specific solid tumor types that will be pursued in the Phase 2 expansion cohort;
  • Report initial clinical results for the second Phase 1 arm of the RTX-240 clinical trial in relapsed/refractory AML;
  • Initiate the Phase 1 clinical trial of RTX-240 in combination with anti-PD-1 therapy in advanced solid tumors in 2H’21;
  • Report initial Phase 1 clinical results for RTX-321 for the treatment of HPV 16-positive cancers by 1Q’22; and
  • Submit an Investigational New Drug Application for RTX-224 by year-end.

Conference Call

The Company will host a conference call and webcast at 8:00 a.m. EDT to discuss this update. The audio webcast will be available on the Events and Presentations page within the Investors and Media section of the Rubius Therapeutics website. The update may also be accessed by dialing 1-800-289-0045 (domestic) or 1-615-622-8086 (international) five minutes prior to the start of the call and providing the passcode 1294064. An archived webcast will be accessible for 90 days after the event.

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