Key Highlights

  • Xencor, Inc. (NASDAQ:XNCR) rose 27.09% to USD 32.00 in early trading on Monday, October 26, 2026, after XmAb819 showed a 45.5% confirmed response rate in kidney cancer in a cohort of 11 patients.
  • ArriVent BioPharma (NASDAQ:AVBP) traded about 18.07% lower near USD 17.20 after ARR-217 showed a 44.8% response rate (13 of 29 patients) in colorectal cancer, following a Phase 3 miss on Tuesday, October 6, 2026.
  • MacroGenics (NASDAQ:MGNX) traded about 11.56% lower near USD 1.99 after interim MGC026 data, and Perspective Therapeutics (NYSEAMERICAN:CATX) fell about 11.49% near USD 1.43 after updated VMT-alpha-NET survival data.
  • The common theme is that response rates between 27% and 47% in small cohorts produced opposite reactions, with funding and safety separating the winner from the three decliners.

Xencor (NASDAQ:XNCR): data that cleared a high bar

Xencor, Inc. (NASDAQ:XNCR) rose 27.09% to USD 32.00 in early trading on Monday, October 26, 2026, from an implied prior close of about USD 25.18 and a market value of about USD 1.87 billion before the move. A company release at 4:35 a.m. ET on Sunday, October 25, 2026 presented Phase 1 dose-selection data for XmAb819, a bispecific antibody that targets ENPP3 on kidney cancer cells and CD3 on T cells. In 68 expansion patients, confirmed objective response rates were 30% at 100 mcg/kg, 44% at 200 mcg/kg and 45.5% at 400 mcg/kg.

The 400 mcg/kg cohort holds 11 patients, so the 45.5% rate is encouraging but statistically fragile. Xencor selected that dose for Phase 3, plans to discuss accelerated approval with the FDA in the first half of 2027 and projects cash into 2029. Grade 3 or higher related events occurred in 72.1% of expansion patients, and 5.9% discontinued treatment. The shares carry less room for disappointment after the rise, and the company is unprofitable.

The accelerated approval path depends on FDA agreement, and the global Phase 3 study against tivozanib, an approved kidney cancer drug, will take years and capital. Xencor expects at least 20 efficacy-evaluable patients at the top dose by the first half of 2027, a larger dataset against which the current 11-patient result will be judged.

ArriVent (NASDAQ:AVBP): an early ADC dataset after a Phase 3 miss

ArriVent BioPharma (NASDAQ:AVBP), a clinical-stage oncology company, traded about 18.07% lower, near USD 17.20, in early trading on Monday, October 26, 2026. The company has not attributed the move to a specific event, but it presented initial Phase 1 data for ARR-217, an antibody-drug conjugate aimed at the CDH17 protein, at the European Society for Medical Oncology congress on Sunday, October 25, 2026. At 6 mg/kg every three weeks, the confirmed response rate in colorectal cancer was 44.8% (13 of 29 patients), and grade 3 or higher treatment-related events occurred in 30.1% of patients across doses.

The shares had already fallen about 47% on Tuesday, October 6, 2026, when the FURVENT Phase 3 trial of firmonertinib missed its primary endpoint, which left pipeline value resting on earlier assets such as ARR-217. Cash and investments were USD 373.1 million at June 30, 2026, with a runway into 2028. A 29-patient sample can be read either way, law firm investigations carry no finding, and the causal link between the data and the fall is an inference.

MacroGenics (NASDAQ:MGNX): interim data meet a cautious market

MacroGenics (NASDAQ:MGNX), a clinical-stage oncology company, traded about 11.56% lower, near USD 1.99, in early trading on Monday, October 26, 2026, and has not issued a release explaining the move. Its release of Friday, October 23, 2026 reported interim Phase 1 results for MGC026, a B7-H3-directed antibody-drug conjugate. Among 17 response-evaluable patients at 6 mg/kg or above, 5 had confirmed responses, or 29%, and in head and neck cancer 6 of 22 patients responded. Grade 3 or higher events affected 51% of all patients and 48% in that cohort.

The company called the results positive, yet the shares fell, which suggests investors had priced in stronger numbers. The release disclosed no cash figures, and a stock near USD 2 may make equity raising more dilutive. Updated head and neck data are not expected until mid-2027, so the next test is distant.

Tolerability is a second concern, since neutropenia affected 27% of patients and anaemia 25%. The company plans a front-line combination cohort with pembrolizumab in early 2027, and competing B7-H3 programmes add a risk for differentiation. Investors should watch the third-quarter results and cash update.

Perspective Therapeutics (NYSEAMERICAN:CATX): survival data without a lift

Perspective Therapeutics (NYSEAMERICAN:CATX), which develops radiopharmaceuticals that deliver radiation directly to tumour cells, traded about 11.49% lower, near USD 1.43, in early trading on Monday, October 26, 2026. The company has not issued a release explaining the move. Updated VMT-alpha-NET data presented at ESMO 2026 and reported on Friday, October 23, 2026 showed a 72% progression-free survival rate at 18 months across the first three cohorts, with response rates of 37% at 20 mCi and 47% at 24 mCi among patients with SSTR2-positive lesions.

No dose-limiting toxicities or grade 4 or 5 events were reported, and the company is preparing an end-of-phase II meeting with the FDA. The risks are a pivotal design that differs from the proposed 20 mCi study, kidney effects in small cohorts and financing, since the update contained no cash position and a stock near USD 1.43 can make new equity costly.

Management said the 20 mCi regimen could support a registrational study and estimates that 60% to 75% of screened patients could fit a narrower population. The highest-grade events were grade 3, and two patients had acute kidney injury. Competition in neuroendocrine tumours from established radioligand products adds pressure, and the company has flagged a North American Neuroendocrine Tumor Society presentation.

Where Things Stand

The answer is that the same conference produced different reactions because investors weighed the size of the response, safety and the cash behind each programme. Xencor (NASDAQ:XNCR) paired a 45.5% response rate with cash into 2029 and a Phase 3 dose, while ArriVent (NASDAQ:AVBP) showed a similar 44.8% rate after a Phase 3 miss and a 47% fall on October 6. MacroGenics (NASDAQ:MGNX) and Perspective Therapeutics (NYSEAMERICAN:CATX) disclosed no cash figures and trade near USD 2 and USD 1.43. The next catalysts are the ArriVent webinar on Monday, October 26, the Fed decision on Wednesday, October 28, 2026, the Xencor FDA discussion in the first half of 2027 and the MacroGenics data in mid-2027. Early cohort data are not guarantees, and this is not investment advice.